Title 49—Transportation--Volume 1
PART 571—FEDERAL MOTOR VEHICLE SAFETY STANDARDS
§ 571.126   Standard No. 126; Electronic stability control systems for light vehicles.
S1. Scope. This standard establishes performance and equipment requirements for electronic stability control (ESC) systems.
S2. Purpose. The purpose of this standard is to reduce the number of deaths and injuries that result from crashes in which the driver loses directional control of the vehicle, including those resulting in vehicle rollover.
S3 Application. This standard applies to passenger cars, multipurpose passenger vehicles, trucks, and buses with a gross vehicle weight rating of 4,536 kilograms (10,000 pounds) or less, according to the phase-in schedule specified in S8 of this standard.
S4. Definitions.
Ackerman Steer Angle means the angle whose tangent is the wheelbase divided by the radius of the turn at a very low speed.
Drive configuration means the driver-selected, or default, condition for distributing power from the engine to the drive wheels (examples include, but are not limited to, 2-wheel drive, front-wheel drive, rear-wheel drive, all-wheel drive, 4-wheel drive high gear with locked differential, and 4-wheel drive low gear).
Electronic stability control system or ESC system means a system that has all of the following attributes:
(1) That augments vehicle directional stability by applying and adjusting the vehicle brake torques individually to induce a correcting yaw moment to a vehicle;
(2) That is computer-controlled with the computer using a closed-loop algorithm to limit vehicle oversteer and to limit vehicle understeer;
(3) That has a means to determine the vehicle's yaw rate and to estimate its side slip or side slip derivative with respect to time;
(4) That has a means to monitor driver steering inputs;
(5) That has an algorithm to determine the need, and a means to modify engine torque, as necessary, to assist the driver in maintaining control of the vehicle; and
(6) That is operational over the full speed range of the vehicle (except at vehicle speeds less than 20 km/h (12.4 mph), when being driven in reverse, or during system initialization).
Lateral acceleration means the component of the vector acceleration of a point in the vehicle perpendicular to the vehicle's x-axis (longitudinal) and parallel to the road plane.
Low-range four-wheel drive configuration means a drive configuration that has the effect of locking the drive gears at the front and rear axles together and providing an additional gear reduction between the engine speed and vehicle speed of at least 2.0.
Mode means an ESC performance algorithm, whether driver-selected or not (examples include, but are not limited to, standard (default) mode, performance mode, snow or slippery road mode, or Off mode).
Oversteer means a condition in which the vehicle's yaw rate is greater than the yaw rate that would occur at the vehicle's speed as a result of the Ackerman Steer Angle.
Side slip or side slip angle means the arctangent of the lateral velocity of the center of gravity of the vehicle divided by the longitudinal velocity of the center of gravity.
Understeer means a condition in which the vehicle's yaw rate is less than the yaw rate that would occur at the vehicle's speed as a result of the Ackerman Steer Angle.
Yaw rate means the rate of change of the vehicle's heading angle measured in degrees/second of rotation about a vertical axis through the vehicle's center of gravity.
S5. Requirements. Subject to the phase-in set forth in S8, each vehicle must be equipped with an ESC system that meets the requirements specified in S5 under the test conditions specified in S6 and the test procedures specified in S7 of this standard.
S5.1 Required Equipment. Vehicles to which this standard applies must be equipped with an electronic stability control system that:
S5.1.1 Is capable of applying brake torques individually to all four wheels and has a control algorithm that utilizes this capability.
S5.1.2 Is operational during all phases of driving including acceleration, coasting, and deceleration (including braking), except when the driver has disabled ESC, the vehicle speed is below 20 km/h (12.4 mph), the vehicle is being driven in reverse, or during system initialization
S5.1.3 Remains capable of activation even if the antilock brake system or traction control system is also activated.
S5.2 Performance Requirements. During each test performed under the test conditions of S6 and the test procedure of S7.9, the vehicle with the ESC system engaged must satisfy the stability criteria of S5.2.1 and S5.2.2, and it must satisfy the responsiveness criterion of S5.2.3 during each of those tests conducted with a commanded steering wheel angle of 5A or greater, where A is the steering wheel angle computed in S7.6.1.
S5.2.1 The yaw rate measured one second after completion of the sine with dwell steering input (time T 0 + 1 in Figure 1) must not exceed 35 percent of the first peak value of yaw rate recorded after the steering wheel angle changes sign (between first and second peaks) (å Peak in Figure 1) during the same test run, and
S5.2.2 The yaw rate measured 1.75 seconds after completion of the sine with dwell steering input must not exceed 20 percent of the first peak value of yaw rate recorded after the steering wheel angle changes sign (between first and second peaks) during the same test run.
S5.2.3 The lateral displacement of the vehicle center of gravity with respect to its initial straight path must be at least 1.83 m (6 feet) for vehicles with a GVWR of 3,500kg (7,716 lb) or less, and 1.52 m (5 feet) for vehicles with a GVWR greater than 3,500 kg (7,716 lb) when computed 1.07 seconds after the Beginning of Steer (BOS). BOS is defined in S7.11.6.
S5.2.3.1 The computation of lateral displacement is performed using double integration with respect to time of the measurement of lateral acceleration at the vehicle center of gravity, as expressed by the formula:
S5.2.3.2 Time t = 0 for the integration operation is the instant of steering initiation, known as the Beginning of Steer (BOS). BOS is defined in S7.11.6.
S5.3 ESC Malfunction. The vehicle must be equipped with a telltale that provides a warning to the driver of the occurrence of one or more malfunctions that affect the generation or transmission of control or response signals in the vehicle's electronic stability control system. When tested according to S7.10, the ESC malfunction telltale:
S5.3.1 As of September 1, 2011, must be mounted inside the occupant compartment in front of and in clear view of the driver;
S5.3.2 As of September 1, 2011, must be identified by the symbol shown for “ESC Malfunction Telltale” or the specified words or abbreviations listed in Table 1 of Standard No. 101 (49 CFR 571.101);
S5.3.3 As of September 1, 2011, except as provided in paragraphs S5.3.4, S5.3.5, S5.3.8, and S5.3.10, the ESC malfunction telltale must illuminate only when a malfunction(s) of the ESC system exists and must remain continuously illuminated under the conditions specified in S5.3 for as long as the malfunction(s) exists (unless the “ESC malfunction” and “ESC Off” telltales are combined in a two-part telltale and the “ESC Off” telltale is illuminated), whenever the ignition locking system is in the “On” (“Run”) position; and
S5.3.4 As of September 1, 2011, except as provided in paragraph S5.3.5, each ESC malfunction telltale must be activated as a check of lamp function either when the ignition locking system is turned to the “On” (“Run”) position when the engine is not running, or when the ignition locking system is in a position between “On” (“Run”) and “Start” that is designated by the manufacturer as a check position.
S5.3.5 The ESC malfunction telltale need not be activated when a starter interlock is in operation.
S5.3.6 The requirement S5.3.4 does not apply to telltales shown in a common space.
S5.3.7 The ESC malfunction telltale must extinguish at the next ignition cycle after the malfunction has been corrected.
S5.3.8 The manufacturer may use the ESC malfunction telltale in a flashing mode to indicate ESC operation.
S5.3.9 Prior to September 1, 2011, a disconnection of the power to the ESC electronic control unit may be indicated by the ABS malfunction telltale instead of the ESC malfunction telltale.
S5.3.10 Manufacturers may use the ESC malfunction telltale in a steady-burning mode to indicate malfunctions of ESC-related systems and functions including traction control, trailer stability assist, corner brake control, and other similar functions that use throttle and/or individual wheel torque control to operate and share common components with the ESC system, and may use the ESC malfunction telltale in a flashing mode to indicate operation of these ESC-related systems.
S5.4 ESC Off and Other System Controls. The manufacturer may include an “ESC Off” control whose only purpose is to place the ESC system in a mode or modes in which it will no longer satisfy the performance requirements of S5.2.1, S5.2.2, and S5.2.3. An “ESC Off” control may be combined with other controls in a multi-function control. Manufacturers may also provide controls for other systems that have an ancillary effect upon ESC operation. Controls of either kind that place the ESC system in a mode in which it will no longer satisfy the performance requirements of S5.2.1, S5.2.2, and S5.2.3 are permitted, provided that:
S5.4.1 The vehicle's ESC system must always return to the manufacturer's original default ESC mode that satisfies the requirements of S5.1 and S5.2 at the initiation of each new ignition cycle, regardless of what ESC mode the driver had previously selected, unless (a) the vehicle is in a low-range four-wheel drive configuration selected by the driver on the previous ignition cycle that is designed for low-speed, off-road driving, or (b) the vehicle is in a four-wheel drive configuration selected by the driver on the previous ignition cycle that is designed for operation at higher speeds on snow-, sand-, or dirt-packed roads and that has the effect of locking the drive gears at the front and rear axles together, provided that the vehicle meets the stability performance requirements of S5.2.1 and S5.2.2 in this mode.
S5.4.2 In addition to the requirements of S5.4.1, if the vehicle's ESC system has more than one ESC mode that satisfies the requirements of S5.1 and S5.2 within the drive configuration selected for the previous ignition cycle, the system must return to the manufacturer's original default ESC mode.
S5.4.3 As of September 1, 2011, a control whose only purpose is to place the ESC system in a mode or modes in which it will no longer satisfy the performance requirements of S5.2.1, S5.2.2, and S5.2.3 must be identified by the symbol shown for “ESC Off” in Table 1 of Standard No. 101 (49 CFR 571.101), or the text, “ESC Off” as listed under “Word(s) or Abbreviations” in Table 1 of Standard No. 101 (49 CFR 571.101).
S5.4.4 A control for another system that has the ancillary effect of placing the ESC system in a mode in which it no longer satisfies the performance requirements of S5.2.1, S5.2.2, and S5.2.3 need not be identified by the “ESC Off” identifiers in Table 1 of Standard No. 101 (49 CFR 571.101), but the ESC status must be identified by the “ESC Off” telltale in accordance with S5.5, as of September 1, 2011, except if the vehicle is in a 4-wheel drive high gear configuration that has the effect of locking the drive gears at the front and rear axles together provided the vehicle meets the stability performance criteria of S5.2.1 and S5.2.2.
S5.5 ESC Off Telltale
S5.5.1 Except as provided in S5.5.10, the vehicle manufacturer must provide a telltale indicating that the vehicle has been put into a mode that renders it unable to satisfy the requirements of S5.2.1, S5.2.2 and S5.2.3, if such a mode is provided.
S5.5.2 As of September 1, 2011, the “ESC Off” telltale must be identified by the symbol shown for “ESC Off” in Table 1 of Standard No. 101 (49 CFR 571.101) or the text, “ESC Off” as listed under “Word(s) or Abbreviations” in Table 1 of Standard No. 101 (49 CFR 571.101).
S5.5.3 As of September 1, 2011, the “ESC Off” telltale must be mounted inside the occupant compartment in front of and in clear view of the driver.
S5.5.4 Except as provided in paragraph S5.4.4, the “ESC Off” telltale must remain continuously illuminated for as long as the ESC is in a mode that renders it unable to satisfy the requirements of S5.2.1, S5.2.2, and S5.2.3, and
S5.5.5 Notwithstanding S5.3.1(e) of 49 CFR 571.101, the vehicle manufacturer may use the “ESC Off” telltale to indicate an ESC level of function other than the fully functional default mode even if the vehicle would meet S5.2.1, S5.2.2 and S5.2.3 at that level of ESC function.
S5.5.6 As of September 1, 2011, except as provided in paragraph S5.5.7 and S5.5.8, each “ESC Off” telltale must be activated as a check of lamp function either when the ignition locking system is turned to the “On” (“Run”) position when the engine is not running, or when the ignition locking system is in a position between “On” (“Run”) and “Start” that is designated by the manufacturer as a check position.
S5.5.7 The “ESC Off” telltale need not be activated when a starter interlock is in operation.
S5.5.8 The requirement S5.5.6 does not apply to telltales shown in a common space.
S5.5.9 The “ESC Off” telltale must extinguish after the ESC system has been returned to its fully functional default mode.
S5.5.10 The “ESC Off” telltale need not illuminate when the vehicle is in a 4-wheel drive high gear locked differential configuration that has the effect of locking the drive gears at the front and rear axles together provided the vehicle meets the stability performance requirements of S5.2.1 and S5.2.2.
S5.6 ESC System Technical Documentation. To ensure a vehicle is equipped with an ESC system that meets the definition of “ESC System” in S4, the vehicle manufacturer must make available to the agency, upon request, the following documentation:
S5.6.1 A system diagram that identifies all ESC system hardware. The diagram must identify what components are used to generate brake torques at each wheel, determine vehicle yaw rate, estimated side slip or the side slip derivative and driver steering inputs.
S5.6.2 A written explanation describing the ESC system basic operational characteristics. This explanation must include a discussion on the system's capability to apply brake torques at each wheel and how the system modifies engine torque during ESC system activation. The explanation must also identify the vehicle speed range and the driving phases (acceleration, deceleration, coasting, during activation of the ABS or traction control) under which the ESC system can activate.
S5.6.3 A logic diagram that supports the explanation provided in S5.6.2.
S5.6.4 Specifically for mitigating vehicle understeer, a discussion of the pertinent inputs to the computer or calculations within the computer and how its algorithm uses that information and controls ESC system hardware to limit vehicle understeer.
S6. Test Conditions.
S6.1 Ambient conditions.
S6.1.1 The ambient temperature is between 7 °C (45 °F) and 40 °C (104 °F).
S6.1.2 The maximum wind speed is no greater than 10 m/s (22 mph) for passenger cars and 5 m/s (11 mph) for multipurpose passenger vehicles, trucks and buses.
S6.2 Road test surface.
S6.2.1 The tests are conducted on a dry, uniform, solid-paved surface. Surfaces with irregularities and undulations, such as dips and large cracks, are unsuitable.
S6.2.2 The road test surface must produce a peak friction coefficient (PFC) of 1.02 when measured using an ASTM F2493 standard reference test tire, in accordance with ASTM E1337-19 (incorporated by reference, see § 571.5) at a speed of 64.4 km/h (40 mph), without water delivery.
S6.2.3 The test surface has a consistent slope between level and 1%.
S6.3 Vehicle conditions.
S6.3.1 The ESC system is enabled for all testing, except when it is turned off directly or by simulating a malfunction in accordance with S7.3 and S7.10, respectively. The ESC system shall be initialized as follows: Place the vehicle in a forward gear and obtain a vehicle speed of 48 ±8 km/h (30 ±5 mph). Drive the vehicle for at least two minutes including at least one left and one right turning maneuver and at least one application of the service brake.
S6.3.2 Test Weight. The vehicle is loaded with the fuel tank filled to at least 75 percent of capacity, and total interior load of 168 kg (370 lbs) comprised of the test driver, approximately 59 kg (130 lbs) of test equipment (automated steering machine, data acquisition system and the power supply for the steering machine), and ballast as required by differences in the weight of test drivers and test equipment. Where required, ballast shall be placed on the floor behind the passenger front seat or if necessary in the front passenger foot well area. All ballast shall be secured in a way that prevents it from becoming dislodged during test conduct.
S6.3.3 Tires. The vehicle is tested with the tires installed on the vehicle at time of initial vehicle sale. The tires are inflated to the vehicle manufacturer's recommended cold tire inflation pressure(s) specified on the vehicle's placard or the tire inflation pressure label. Tubes may be installed to prevent tire de-beading.
S6.3.4 Outriggers. Outriggers are used for testing trucks, multipurpose passenger vehicles, and buses. Vehicles with a baseline weight less than 1,588 kg (3,500 lbs) are equipped with “light” outriggers. Vehicles with a baseline weight equal to or greater than 1,588 kg (3,500 lbs) and less than 2,722 kg (6,000 lbs) are equipped with “standard” outriggers. Vehicles with a baseline weight equal to or greater than 2,722 kg (6,000 lbs) are equipped with “heavy” outriggers. A vehicle's baseline weight is the weight of the vehicle delivered from the dealer, fully fueled, with a 73 kg (160 lb) driver. Light outriggers are designed with a maximum weight of 27 kg (59.5 lb) and a maximum roll moment of inertia of 27 kg-m 2 (19.9 ft-lb-sec 2 ). Standard outriggers are designed with a maximum weight of 32 kg (70 lb) and a maximum roll moment of inertia of 35.9 kg-m 2 (26.5 ft-lb-sec 2 ). Heavy outriggers are designed with a maximum weight of 39 kg (86 lb) and a maximum roll moment of inertia of 40.7 kg-m 2 (30.0 ft-lb-sec 2 ).
S6.3.5 Automated steering machine. A steering machine programmed to execute the required steering pattern must be used in S7.5.2, S7.5.3, S7.6 and S7.9. The steering machine shall be capable of supplying steering torques between 40 to 60 Nm (29.5 to 44.3 lb-ft). The steering machine must be able to apply these torques when operating with steering wheel velocities up to 1200 degrees per second.
S7. Test Procedure.
S7.1 Inflate the vehicles' tires to the cold tire inflation pressure(s) provided on the vehicle's placard or the tire inflation pressure label.
S7.2 Telltale bulb check. With the vehicle stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “On” (“Run”) position or, where applicable, the appropriate position for the lamp check. The ESC malfunction telltale must be activated as a check of lamp function, as specified in S5.3.4, and if equipped, the “ESC Off” telltale must also be activated as a check of lamp function, as specified in S5.5.6. The telltale bulb check is not required for a telltale shown in a common space as specified in S5.3.6 and S5.5.8.
S7.3 “ESC Off” control check. For vehicles equipped with an “ESC Off” control, with the vehicle stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “On” (“Run”) position. Activate the “ESC Off” control and verify that the “ESC Off” telltale is illuminated, as specified in S5.5.4. Turn the ignition locking system to the “Lock” or “Off” position. Again, activate the ignition locking system to the “On” (“Run”) position and verify that the “ESC Off” telltale has extinguished indicating that the ESC system has been reactivated as specified in S5.4.1.
S7.4 Brake Conditioning. Condition the vehicle brakes as follows:
S7.4.1 Ten stops are performed from a speed of 56 km/h (35 mph), with an average deceleration of approximately 0.5 g.
S7.4.2 Immediately following the series of 56 km/h (35 mph) stops, three additional stops are performed from 72 km/h (45 mph).
S7.4.3 When executing the stops in S7.4.2, sufficient force is applied to the brake pedal to activate the vehicle's antilock brake system (ABS) for a majority of each braking event.
S7.4.4 Following completion of the final stop in S7.4.2, the vehicle is driven at a speed of 72 km/h (45 mph) for five minutes to cool the brakes.
S7.5 Tire Conditioning. Condition the tires using the following procedure to wear away mold sheen and achieve operating temperature immediately before beginning the test runs of S7.6 and S7.9.
S7.5.1 The test vehicle is driven around a circle 30 meters (100 feet) in diameter at a speed that produces a lateral acceleration of approximately 0.5 to 0.6 g for three clockwise laps followed by three counterclockwise laps.
S7.5.2 Using a sinusoidal steering pattern at a frequency of 1 Hz, a peak steering wheel angle amplitude corresponding to a peak lateral acceleration of 0.5-0.6 g, and a vehicle speed of 56 km/h (35 mph), the vehicle is driven through four passes performing 10 cycles of sinusoidal steering during each pass.
S7.5.3 The steering wheel angle amplitude of the final cycle of the final pass is twice that of the other cycles. The maximum time permitted between all laps and passes is five minutes.
S7.6 Slowly Increasing Steer Test. The vehicle is subjected to two series of runs of the Slowly Increasing Steer Test using a constant vehicle speed of 80 ±2 km/h (50 ±1 mph) and a steering pattern that increases by 13.5 degrees per second until a lateral acceleration of approximately 0.5 g is obtained. Three repetitions are performed for each test series. One series uses counterclockwise steering, and the other series uses clockwise steering. The maximum time permitted between each test run is five minutes.
S7.6.1 From the Slowly Increasing Steer tests, the quantity “A” is determined. “A” is the steering wheel angle in degrees that produces a steady state lateral acceleration (corrected using the methods specified in S7.11.3) of 0.3 g for the test vehicle. Utilizing linear regression, A is calculated, to the nearest 0.1 degrees, from each of the six Slowly Increasing Steer tests. The absolute value of the six A's calculated is averaged and rounded to the nearest 0.1 degrees to produce the final quantity, A, used below.
S7.7 After the quantity A has been determined, without replacing the tires, the tire conditioning procedure described in S7.5 is performed immediately prior to conducting the Sine with Dwell Test of S7.9. Initiation of the first Sine with Dwell test series shall begin within two hours after completion of the Slowly Increasing Steer tests of S7.6.
S7.8 Check that the ESC system is enabled by ensuring that the ESC malfunction and “ESC Off” (if provided) telltales are not illuminated.
S7.9 Sine with Dwell Test of Oversteer Intervention and Responsiveness. The vehicle is subjected to two series of test runs using a steering pattern of a sine wave at 0.7 Hz frequency with a 500 ms delay beginning at the second peak amplitude as shown in Figure 2 (the Sine with Dwell tests). One series uses counterclockwise steering for the first half cycle, and the other series uses clockwise steering for the first half cycle. The vehicle is provided a cool-down period between each test run of 90 seconds to five minutes, with the vehicle stationary.
S7.9.1 The steering motion is initiated with the vehicle coasting in high gear at 80 ±2 km/h (50 ±1 mph).
S7.9.2 In each series of test runs, the steering amplitude is increased from run to run, by 0.5A, provided that no such run will result in a steering amplitude greater than that of the final run specified in S7.9.4.
S7.9.3 The steering amplitude for the initial run of each series is 1.5A where A is the steering wheel angle determined in S7.6.1.
S7.9.4 The steering amplitude of the final run in each series is the greater of 6.5A or 270 degrees, provided the calculated magnitude of 6.5A is less than or equal to 300 degrees. If any 0.5A increment, up to 6.5A, is greater than 300 degrees, the steering amplitude of the final run shall be 300 degrees.
S7.9.5 Upon completion of the two series of test runs, post processing of yaw rate and lateral acceleration data is done as specified in S7.11.
S7.10 ESC Malfunction Detection.
S7.10.1 Simulate one or more ESC malfunction(s) by disconnecting the power source to any ESC component, or disconnecting any electrical connection between ESC components (with the vehicle power off). When simulating an ESC malfunction, the electrical connections for the telltale lamp(s) are not to be disconnected.
S7.10.2 With the vehicle initially stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “Start” position and start the engine. Place the vehicle in a forward gear and obtain a vehicle speed of 48 ±8 km/h (30 ±5 mph). Drive the vehicle for at least two minutes including at least one left and one right turning maneuver and at least one application of the service brake. Verify that within two minutes after obtaining this vehicle speed the ESC malfunction indicator illuminates in accordance with S5.3.
S7.10.3 As of September 1, 2011, stop the vehicle, deactivate the ignition locking system to the “Off” or “Lock” position. After a five-minute period, activate the vehicle's ignition locking system to the “Start” position and start the engine. Verify that the ESC malfunction indicator again illuminates to signal a malfunction and remains illuminated as long as the engine is running or until the fault is corrected.
S7.10.4 Deactivate the ignition locking system to the “Off” or “Lock” position. Restore the ESC system to normal operation, activate the ignition system to the “Start” position and start the engine. Place the vehicle in a forward gear and obtain a vehicle speed of 48 ±8 km/h (30 ±5 mph). Drive the vehicle for at least two minutes including at least one left and one right turning maneuver and at least one application of the service brake. Verify that within two minutes after obtaining this vehicle speed that the ESC malfunction indicator has extinguished.
S7.11 Post Data Processing—Calculations for Performance Metrics. Yaw rate and lateral displacement measurements and calculations must be processed utilizing the following techniques:
S7.11.1 Raw steering wheel angle data is filtered with a 12-pole phaseless Butterworth filter and a cutoff frequency of 10Hz. The filtered data is then zeroed to remove sensor offset utilizing static pretest data.
S7.11.2 Raw yaw rate data is filtered with a 12-pole phaseless Butterworth filter and a cutoff frequency of 6Hz. The filtered data is then zeroed to remove sensor offset utilizing static pretest data.
S7.11.3 Raw lateral acceleration data is filtered with a 12-pole phaseless Butterworth filter and a cutoff frequency of 6Hz. The filtered data is then zeroed to remove sensor offset utilizing static pretest data. The lateral acceleration data at the vehicle center of gravity is determined by removing the effects caused by vehicle body roll and by correcting for sensor placement via use of coordinate transformation. For data collection, the lateral accelerometer shall be located as close as possible to the position of the vehicle's longitudinal and lateral centers of gravity.
S7.11.4 Steering wheel velocity is determined by differentiating the filtered steering wheel angle data. The steering wheel velocity data is then filtered with a moving 0.1 second running average filter.
S7.11.5 Lateral acceleration, yaw rate and steering wheel angle data channels are zeroed utilizing a defined “zeroing range.” The methods used to establish the zeroing range are defined in S7.11.5.1 and S7.11.5.2.
S7.11.5.1 Using the steering wheel rate data calculated using the methods described in S7.11.4, the first instant steering wheel rate exceeds 75 deg/sec is identified. From this point, steering wheel rate must remain greater than 75 deg/sec for at least 200 ms. If the second condition is not met, the next instant steering wheel rate exceeds 75 deg/sec is identified and the 200 ms validity check applied. This iterative process continues until both conditions are ultimately satisfied.
S7.11.5.2 The “zeroing range” is defined as the 1.0 second time period prior to the instant the steering wheel rate exceeds 75 deg/sec ( i.e. , the instant the steering wheel velocity exceeds 75 deg/sec defines the end of the “zeroing range”).
S7.11.6 The Beginning of Steer (BOS) is defined as the first instance filtered and zeroed steering wheel angle data reaches −5 degrees (when the initial steering input is counterclockwise) or + 5 degrees (when the initial steering input is clockwise) after time defining the end of the “zeroing range.” The value for time at the BOS is interpolated.
S7.11.7 The Completion of Steer (COS) is defined as the time the steering wheel angle returns to zero at the completion of the Sine with Dwell steering maneuver. The value for time at the zero degree steering wheel angle is interpolated.
S7.11.8 The second peak yaw rate is defined as the first local yaw rate peak produced by the reversal of the steering wheel. The yaw rates at 1.000 and 1.750 seconds after COS are determined by interpolation.
S7.11.9 Determine lateral velocity by integrating corrected, filtered and zeroed lateral acceleration data. Zero lateral velocity at BOS event. Determine lateral displacement by integrating zeroed lateral velocity. Zero lateral displacement at BOS event. Lateral displacement at 1.07 seconds from BOS event is determined by interpolation.
S8. Phase-in schedule.
S8.1 Vehicles manufactured on or after September 1, 2008, and before September 1, 2009. For vehicles manufactured on or after September 1, 2008, and before September 1, 2009, the number of vehicles complying with this standard must not be less than 55 percent of:
(a) The manufacturer's average annual production of vehicles manufactured on or after September 1, 2005, and before September 1, 2008; or
(b) The manufacturer's production on or after September 1, 2008, and before September 1, 2009.
S8.2 Vehicles manufactured on or after September 1, 2009, and before September 1, 2010. For vehicles manufactured on or after September 1, 2009, and before September 1, 2010, the number of vehicles complying with this standard must not be less than 75 percent of:
(a) The manufacturer's average annual production of vehicles manufactured on or after September 1, 2006, and before September 1, 2009; or
(b) The manufacturer's production on or after September 1, 2009, and before September 1, 2010.
S8.3 Vehicles manufactured on or after September 1, 2010, and before September 1, 2011. For vehicles manufactured on or after September 1, 2010, and before September 1, 2011, the number of vehicles complying with this standard must not be less than 95 percent of:
(a) The manufacturer's average annual production of vehicles manufactured on or after September 1, 2007, and before September 1, 2010; or
(b) The manufacturer's production on or after September 1, 2010, and before September 1, 2011.
S8.4 Vehicles manufactured on or after September 1, 2011. All vehicles manufactured on or after September 1, 2011 must comply with this standard.
S8.5 Calculation of complying vehicles.
(a) For purposes of complying with S8.1, a manufacturer may count a vehicle if it is certified as complying with this standard and is manufactured on or after June 5, 2007, but before September 1, 2009.
(b) For purpose of complying with S8.2, a manufacturer may count a vehicle if it:
(1)(i) Is certified as complying with this standard and is manufactured on or after June 5, 2007, but before September 1, 2010; and
(ii) Is not counted toward compliance with S8.1; or
(2) Is manufactured on or after September 1, 2009, but before September 1, 2010.
(c) For purposes of complying with S8.3, a manufacturer may count a vehicle if it:
(1)(i) Is certified as complying with this standard and is manufactured on or after June 5, 2007, but before September 1, 2011; and
(ii) Is not counted toward compliance with S8.1 or S8.2; or
(2) Is manufactured on or after September 1, 2010, but before September 1, 2011.
S8.6 Vehicles produced by more than one manufacturer.
S8.6.1 For the purpose of calculating average annual production of vehicles for each manufacturer and the number of vehicles manufactured by each manufacturer under S8.1 through S8.4, a vehicle produced by more than one manufacturer must be attributed to a single manufacturer as follows, subject to S8.6.2:
(a) A vehicle that is imported must be attributed to the importer.
(b) A vehicle manufactured in the United States by more than one manufacturer, one of which also markets the vehicle, must be attributed to the manufacturer that markets the vehicle.
S8.6.2 A vehicle produced by more than one manufacturer must be attributed to any one of the vehicle's manufacturers specified by an express written contract, reported to the National Highway Traffic Safety Administration under 49 CFR Part 585, between the manufacturer so specified and the manufacturer to which the vehicle would otherwise be attributed under S8.6.1.
S8.7 Small volume manufacturers.
Vehicles manufactured during any of the three years of the September 1, 2008 through August 31, 2011 phase-in by a manufacturer that produces fewer than 5,000 vehicles for sale in the United States during that year are not subject to the requirements of S8.1, S8.2, S8.3, and S8.5.
S8.8 Final-stage manufacturers and alterers.
Vehicles that are manufactured in two or more stages or that are altered (within the meaning of 49 CFR 567.7) after having previously been certified in accordance with part 567 of this chapter are not subject to the requirements of S8.1 through S8.5. Instead, all vehicles produced by these manufacturers on or after September 1, 2012 must comply with this standard.
§ 571.127   Standard No. 127; Automatic emergency braking systems for light vehicles.
S1. Scope. This standard establishes performance requirements for automatic emergency braking (AEB) systems for light vehicles.
S2. Purpose. The purpose of this standard is to reduce the number of deaths and injuries that result from crashes in which drivers do not apply the brakes or fail to apply sufficient braking power to avoid or mitigate a crash.
S3. Application. This standard applies to passenger cars and to multipurpose passenger vehicles, trucks, and buses with a gross vehicle weight rating (GVWR) of 4,536 kilograms (10,000 pounds) or less.
S4. Definitions.
Adaptive cruise control system is an automatic speed control system that allows the equipped vehicle to follow a lead vehicle at a pre-selected gap by controlling the engine, power train, and service brakes.
Ambient illumination is the illumination as measured at the test surface, not including any illumination provided by the subject vehicle.
Automatic emergency braking ( AEB) system is a system that detects an imminent collision with vehicles, objects, and road users in or near the path of a vehicle and automatically controls the vehicle's service brakes to avoid or mitigate the collision.
Brake pedal application onset is when 11 N of force has been applied to the brake pedal.
Forward collision warning is an auditory and visual warning provided to the vehicle operator by the AEB system that is designed to induce immediate forward crash avoidance response by the vehicle operator.
Forward collision warning onset is the first moment in time when a forward collision warning is provided.
Headway is the distance between the subject vehicle's frontmost plane normal to its centerline and as applicable: the vehicle test device's rearmost plane normal to its centerline; a parallel contact plane (to the subject vehicle's frontmost plane) on the pedestrian test mannequin; and the leading edge of the steel trench plate.
Lead vehicle is a vehicle test device facing the same direction and preceding a subject vehicle within the same travel lane.
Lead vehicle braking onset is the point at which the lead vehicle achieves a deceleration of 0.05 g due to brake application.
Pedestrian test mannequin is a device used during AEB testing, when approaching pedestrians, meeting the specifications of subpart B of 49 CFR part 596.
Small-volume manufacturer means an original vehicle manufacturer that produces or assembles fewer than 5,000 vehicles annually for sale in the United States.
Steel trench plate is a rectangular steel plate often used in road construction to temporarily cover sections of pavement unsafe to drive over directly.
Subject vehicle is the vehicle under examination for compliance with this standard.
Travel path is the path projected onto the road surface of a point located at the intersection of the subject vehicle's frontmost vertical plane and longitudinal vertical center plane, as the subject vehicle travels forward.
Subject vehicle braking onset is the point at which the subject vehicle achieves a deceleration of 0.15 g due to the automatic control of the service brakes.
Vehicle test device is a device meeting the specifications set forth in subpart C of 49 CFR part 596.
S5. Requirements.
(a) Except as provided in S5(b), vehicles manufactured on or after September 1, 2029 must meet the requirements of this standard.
(b) The requirements of S5(a) do not apply to small-volume manufacturers, final-stage manufacturers, and alterers until one year after the dates specified in S5(a).
S5.1. Requirements when approaching a lead vehicle.
S5.1.1. Forward collision warning. A vehicle is required to have a forward collision warning system, as defined in S4 that provides an auditory and visual signal to the driver of an impending collision with a lead vehicle. The system must operate under the conditions specified in S6 when traveling at any forward speed that is greater than 10 km/h (6.2 mph) and less than 145 km/h (90.1 mph).
(a) Auditory signal.
(1) The auditory signal must have a high fundamental frequency of at least 800 Hz.
(2) The auditory signal must have a tempo in the range of 6-12 pulses per second and a duty cycle in the range of 0.25-0.95.
(3) The auditory signal as measured adjacent to a 50th percentile male driver's right ear (tragion) must have an intensity of 15-30 dB above the average noise level inside the vehicle when measured over a 5-second period under the range of test conditions specified in S6, at 100 km/h, with all vehicle openings closed, and all subject vehicle audio and sound-producing systems or functions that are not necessary for performing tests pursuant to the conditions in S6 and the procedures in S7, S8, S9 of this standard set to off.
(4) In-vehicle audio that is not related to a crash avoidance system warning must be muted, or reduced in volume during presentation of the FCW auditory signal to within 5 dB of the average noise level inside the vehicle (as measured in S5.1.1(a)(3)), for the duration of the first between-pulse period of the FCW auditory signal under the range of test conditions specified in S6, at 100 km/h, with all vehicle openings closed, and all subject vehicle audio and sound-producing systems or functions that are not necessary for performing tests pursuant to the conditions in S6 and the procedures in S7, S8, S9 of this standard set to off.
(b) Visual signal.
(1) The visual signal symbol must be located within an ellipse that extends ±18 degrees vertically and ±10 degrees horizontally of the driver forward line of sight based on the forward-looking eye midpoint (M f ) as described in S14 of 49 CFR 571.111.
(2) The visual signal must include the crash pictorial symbol in SAE J2400, 4.1.16, incorporated by reference (see § 571.5).
(3) The visual signal symbol must be red in color and steady burning.
S5.1.2. Automatic emergency braking. A vehicle is required to have an automatic emergency braking system, as defined in S4, that applies the service brakes automatically when a collision with a lead vehicle is imminent. The system must operate under the conditions specified in S6 when the vehicle is traveling at any forward speed that is greater than 10 km/h (6.2 mph) and less than 145 km/h (90.1 mph).
S5.1.3. Performance test requirements. The vehicle must provide a forward collision warning and subsequently apply the service brakes automatically such that the subject vehicle does not collide with the lead vehicle when tested using the procedures in S7 under the conditions specified in S6. The forward collision warning is not required if adaptive cruise control is engaged.
S5.2. Requirements when approaching pedestrians.
S5.2.1. Forward collision warning. A vehicle is required to have a forward collision warning system, as defined in S4, that provides an auditory and visual signal to the driver of an impending collision with a pedestrian. The system must operate under the conditions specified in S6 when the vehicle is traveling at any forward speed that is greater than 10 km/h (6.2 mph) and less than 73 km/h (45.3 mph). The forward collision warning system must meet the auditory signal and visual signal requirements specified in S5.1.1.
S5.2.2. Automatic emergency braking. A vehicle is required to have an automatic emergency braking system, as defined in S4, that applies the service brakes automatically when a collision with a pedestrian is imminent when the vehicle is under the conditions specified in S6 and is traveling at any forward speed that is greater than 10 km/h (6.2 mph) and less than 73 km/h (45.3 mph).
S5.2.3. Performance test requirements. The vehicle must provide a forward collision warning and apply the brakes automatically such that the subject vehicle does not collide with the pedestrian test mannequin when tested using the procedures in S8 under the conditions specified in S6.
S5.3. False activation. The vehicle must not automatically apply braking that results in peak additional deceleration that exceeds what manual braking would produce by 0.25 g or greater, when tested using the procedures in S9 under the conditions specified in S6.
S5.4. Malfunction detection and controls.
S5.4.1 The system must continuously detect system malfunctions, including performance degradation caused solely by sensor obstructions. If the system detects a malfunction, or if the system adjusts its performance such that it will not meet the requirements specified in S5.1, S5.2, or S5.3, the system must provide the vehicle operator with a telltale notification.
S5.4.2 Except as provided in S5.4.2.1 and S5.4.2.2, the manufacturer must not provide a control that will place the AEB system in a mode or modes in which it will no longer satisfy the performance requirements of S5.1, S5.2, and S5.3.
S5.4.2.1 The manufacturer may provide a control to allow AEB deactivation that is securely activated, provided the manufacturer enables such activation exclusively in a vehicle owned by a law enforcement agency.
S5.4.2.2 The manufacturer may allow AEB deactivation to occur during low-range four-wheel drive configurations, when the driver selects “tow mode,” or when another vehicle system is activated that will have a negative ancillary impact on AEB operation.
S5.4.3 The vehicle's AEB system must always return to the manufacturer's original default AEB mode that satisfies the requirements of S5.1, S5.2, and S5.3 at the initiation of each new ignition cycle, unless the vehicle is in a low-range four-wheel drive configuration selected by the driver on the previous ignition cycle designed for low-speed, off-road driving.
S6. Test conditions.
S6.1. Environmental conditions.
S6.1.1. Temperature. The ambient temperature is any temperature between 0 °C and 40 °C.
S6.1.2. Wind. The maximum wind speed is no greater than 10 m/s (22 mph) during lead vehicle avoidance tests and 6.7 m/s (15 mph) during pedestrian avoidance tests.
S6.1.3. Ambient lighting.
(a) Daylight testing.
(1) The ambient illumination on the test surface is any level at or above 2,000 lux.
(2) Testing is not performed while driving toward or away from the sun such that the horizontal angle between the sun and a vertical plane containing the centerline of the subject vehicle is less than 25 degrees and the solar elevation angle is less than 15 degrees.
(b) Dark testing.
(1) The ambient illumination on the test surface is any level at or below 0.2 lux.
(2) Testing is performed under any lunar phase.
(3) Testing is not performed while driving toward the moon such that the horizontal angle between the moon and a vertical plane containing the centerline of the subject vehicle is less than 25 degrees and the lunar elevation angle is less than 15 degrees.
S6.1.4. Precipitation. Testing is not conducted during periods of precipitation or when visibility is affected by fog, smoke, ash, or other particulate.
S6.2. Road conditions.
S6.2.1. Test Track surface and construction. The tests are conducted on a dry, uniform, solid-paved surface. Surfaces with debris, irregularities, or undulations, such as loose pavement, large cracks, or dips may not be used.
S6.2.2. Surface friction. The road test surface produces a peak friction coefficient (PFC) of 1.02 when measured using an ASTM F2493 standard reference test tire, in accordance with ASTM E1337-19 (incorporated by reference, see §  571.5), at a speed of 64 km/h (40 mph), without water delivery.
S6.2.3. Slope. The test surface has any consistent slope between 0 percent and 1 percent.
S6.2.4. Markings. The road surface within 2 m of the intended travel path is marked with zero, one, or two lines of any configuration or color. If one line is used, it is straight. If two lines are used, they are straight, parallel to each other, and at any distance from 2.7 m to 4.5 m apart.
S6.2.5. Obstructions. Testing is conducted such that the vehicle does not travel beneath any overhead structures, including but not limited to overhead signs, bridges, or gantries. No vehicles, obstructions, or stationary objects are within 7.4 m of either side of the intended travel path except as specified.
S6.3. Subject vehicle conditions.
S6.3.1. Malfunction notification. Testing is not conducted while the AEB malfunction telltale specified in S5.4 is illuminated.
S6.3.2. Sensor obstruction. All sensors used by the system and any part of the vehicle immediately ahead of the sensors, such as plastic trim, the windshield, etc., are free of debris or obstructions.
S6.3.3. Tires. The vehicle is equipped with the original tires present at the time of initial sale. The tires are inflated to the vehicle manufacturer's recommended cold tire inflation pressure(s) specified on the vehicle's placard or the tire inflation pressure label.
S6.3.4. Brake burnish.
(a) Vehicles subject to § 571.105 are burnished in accordance with S7.4 of § 571.105.
(b) Vehicles subject to § 571.135 are burnished in accordance with S7.1 of § 571.135.
S6.3.5. Brake temperature. The average temperature of the service brakes on the hottest axle of the vehicle during testing, measured according to S6.4.1 of § 571.135, is between 65 °C and 100 °C prior to braking.
S6.3.6. Fluids. All non-consumable fluids for the vehicle are at 100 percent capacity. All consumable fluids are at any level from 5 to 100 percent capacity.
S6.3.7. Propulsion battery charge. The propulsion batteries are charged at any level from 5 to 100 percent capacity.
S6.3.8. Cruise control. Cruise control, including adaptive cruise control, is configured under any available setting.
S6.3.9. Adjustable forward collision warning. Forward collision warning is configured in any operator-configurable setting.
S6.3.10. Engine braking. A vehicle equipped with an engine braking system that is engaged and disengaged by the operator is tested with the system in any selectable configuration.
S6.3.11. Regenerative braking. Regenerative braking is configured under any available setting.
S6.3.12. Headlamps.
(a) Daylight testing is conducted with the headlamp control in any selectable position.
(b) Darkness testing is conducted with the vehicle's lower beams active and separately with the vehicle's upper beams active.
(c) Prior to performing darkness testing, headlamps are aimed according to the vehicle manufacturer's instructions. The weight of the loaded vehicle at the time of headlamp aiming is within 10 kg of the weight of the loaded vehicle during testing.
S6.3.13. Subject vehicle loading. The vehicle load, which is the sum of any vehicle occupants and any test equipment and instrumentation, does not exceed 277 kg. The load does not cause the vehicle to exceed its GVWR or any axle to exceed its GAWR.
S6.3.14. AEB system initialization. The vehicle is driven at a speed of 10 km/h or higher for at least one minute prior to testing, and subsequently the starting system is not cycled off prior to testing.
S6.4. Equipment and test devices.
S6.4.1. The vehicle test device is specified in 49 CFR part 596, subpart C. Local fluttering of the lead vehicle's external surfaces does not exceed 10 mm perpendicularly from the reference surface, and distortion of the lead vehicle's overall shape does not exceed 25 mm in any direction.
S6.4.2. Adult pedestrian test mannequin is specified in 49 CFR part 596, subpart B.
S6.4.3. Child pedestrian test mannequin is specified in 49 CFR part 596, subpart B.
S6.4.4. The steel trench plate used for the false activation test has the dimensions 2.4 m x 3.7 m x 25 mm and is made of ASTM A36 steel. Any metallic fasteners used to secure the steel trench plate are flush with the top surface of the steel trench plate.
S7. Testing when approaching a lead vehicle.
S7.1. Setup.
(a) The testing area is set up in accordance with figure 2 to this section.
(b) Testing is conducted during daylight.
(c) For reference, table 1 to S7.1 specifies the subject vehicle speed (V SV ), lead vehicle speed (V LV ), headway, and lead vehicle deceleration for each test that may be conducted.
(d) The intended travel path of the vehicle is a straight line toward the lead vehicle from the location corresponding to a headway of L 0 .
(e) If the road surface is marked with a single or double lane line, the intended travel path is parallel to and 1.8 m from the inside of the closest line. If the road surface is marked with two lane lines bordering the lane, the intended travel path is centered between the two lines.
(f) For each test run conducted, the subject vehicle speed (V SV ), lead vehicle speed (V LV ), headway, and lead vehicle deceleration will be selected from the ranges specified in table 1 to S7.1.
Table 1 to S7.1—Test Parameters When Approaching a Lead Vehicle
S7.2. Headway calculation. For each test run conducted under S7.3 and S7.4, the headway ( L 0 ), in meters, providing 5.0 seconds time to collision ( TTC ) is calculated. L 0 is determined with the following equation where V SV is the speed of the subject vehicle in m/s and V LV is the speed of the lead vehicle in m/s:
S7.3. Stopped lead vehicle.
S7.3.1. Test parameters.
(a) For testing with no subject vehicle manual brake application, the subject vehicle test speed is any speed between 10 km/h and 80 km/h, and the lead vehicle speed is 0 km/h.
(b) For testing with manual brake application of the subject vehicle, the subject vehicle test speed is any speed between 70 km/h and 100 km/h, and the lead vehicle speed is 0 km/h.
S7.3.2. Test conduct prior to forward collision warning onset.
(a) The lead vehicle is placed stationary with its longitudinal centerline coincident to the intended travel path.
(b) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(c) The subject vehicle approaches the rear of the lead vehicle.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(e) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering input such that the travel path does not deviate more than 0.3 m laterally from the intended travel path and the subject vehicle's yaw rate does not exceed ±1.0 deg/s.
S7.3.3. Test conduct after forward collision warning onset.
(a) The accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles tested with cruise control active.
(b) For testing conducted with manual brake application, the service brakes are applied as specified in S10. The onset of brake pedal application occurs 1.0 ± 0.1 second after forward collision warning onset.
(c) For testing conducted without manual brake application, no manual brake application is made until the test completion criteria of S7.3.4 are satisfied.
S7.3.4. Test completion criteria. The test run is complete when the subject vehicle comes to a complete stop without making contact with the lead vehicle or when the subject vehicle makes contact with the lead vehicle.
S7.4. Slower-moving lead vehicle.
S7.4.1. Test parameters.
(a) For testing with no subject vehicle manual brake application, the subject vehicle test speed is any speed between 40 km/h and 80 km/h, and the lead vehicle speed is 20 km/h.
(b) For testing with manual brake application of the subject vehicle, the subject vehicle test speed is any speed between 70 km/h and 100 km/h, and the lead vehicle speed is 20 km/h.
S7.4.2. Test conduct prior to forward collision warning onset.
(a) The lead vehicle is propelled forward in a manner such that the longitudinal center plane of the lead vehicle does not deviate laterally more than 0.3m from the intended travel path.
(b) The subject vehicle approaches the lead vehicle.
(c) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle and lead vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(e) Beginning when the headway corresponds to L 0 , the subject vehicle and lead vehicle headings are be maintained with minimal steering input such that the subject vehicle's travel path does not deviate more than 0.3 m laterally from the centerline of the lead vehicle, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s prior to the forward collision warning onset.
S7.4.3. Test conduct after forward collision warning onset.
(a) The subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles tested with cruise control active.
(b) For testing conducted with manual braking application, the service brakes are applied as specified in S10. The onset of brake pedal application is 1.0 ±0.1 second after the forward collision warning onset.
(c) For testing conducted without manual braking application, no manual brake application is made until the test completion criteria of S7.4.4 are satisfied.
S7.4.4. Test completion criteria. The test run is complete when the subject vehicle speed is less than or equal to the lead vehicle speed without making contact with the lead vehicle or when the subject vehicle makes contact with the lead vehicle.
S7.5. Decelerating lead vehicle.
S7.5.1. Test parameters.
(a) The subject vehicle test speed is 50 km/h or 80 km/h, and the lead vehicle speed is identical to the subject vehicle test speed.
(b) [Reserved]
S7.5.2. Test conduct prior to lead vehicle braking onset.
(a) Before the 3 seconds prior to lead vehicle braking onset, the subject vehicle is be driven at any speed, in any direction, on any road surface, for any amount of time.
(b) Between 3 seconds prior to lead vehicle braking onset and lead vehicle braking onset:
(1) The lead vehicle is propelled forward in a manner such that the longitudinal center plane of the vehicle does not deviate laterally more than 0.3 m from the intended travel path.
(2) The subject vehicle follows the lead vehicle at a headway of any distance between 12 m and 40 m.
(3) The subject vehicle's speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs prior to forward collision warning onset.
(4) The lead vehicle's speed is maintained within 1.6 km/h.
(5) The subject vehicle and lead vehicle headings are maintained with minimal steering input such that their travel paths do not deviate more than 0.3 m laterally from the centerline of the lead vehicle, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s until onset of forward collision warning.
S7.5.3. Test conduct following lead vehicle braking onset.
(a) The lead vehicle is decelerated to a stop with a targeted average deceleration of any value between 0.3g and 0.5g. The targeted deceleration magnitude is achieved within 1.5 seconds of lead vehicle braking onset and is maintained until 250 ms prior to coming to a stop.
(b) After forward collision warning onset, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles with cruise control active.
(c) For testing conducted with manual braking application, the service brakes are applied as specified in S10. The brake pedal application onset occurs 1.0 ± 0.1 second after the forward collision warning onset.
(d) For testing conducted without manual braking application, no manual brake application is made until the test completion criteria of S7.5.4 are satisfied.
S7.5.4. Test completion criteria. The test run is complete when the subject vehicle comes to a complete stop without making contact with the lead vehicle or when the subject vehicle makes contact with the lead vehicle.
S8. Testing when approaching a pedestrian.
S8.1. Setup.
S8.1.1. General.
(a) For reference, table 2 to S8.1.1 specifies the pedestrian test mannequin direction of travel, overlap, obstruction condition and speed (V P ), the subject vehicle speed (V SV ), and the lighting condition for each test that may be conducted.
(b) The intended travel path of the vehicle is a straight line originating at the location corresponding to a headway of L 0 .
(c) If the road surface is marked with a single or double lane line, the intended travel path is parallel to and 1.8 m from the inside of the closest line. If the road surface is marked with two lane lines bordering the lane, the intended travel path is centered between the two lines.
(d) For each test run conducted, the subject vehicle speed (V SV ) will be selected from the range specified in table 2 to S8.1.1.
Table 2 to S8.1.1—Test Parameters When Approaching a Pedestrian
S8.1.2. Overlap. As depicted in figure 1 to this section, overlap describes the location of the point on the front of the subject vehicle that would make contact with a pedestrian if no braking occurred. Overlap is the percentage of the subject vehicle's overall width that the pedestrian test mannequin traverses. It is measured from the right or the left, depending on the side of the subject vehicle where the pedestrian test mannequin originates. For each test run, the actual overlap will be within 0.15 m of the specified overlap.
S8.1.3. Pedestrian test mannequin.
(a) For testing where the pedestrian test mannequin is secured to a moving apparatus, the pedestrian test mannequin is secured so that it faces the direction of motion. The pedestrian test mannequin leg articulation starts on apparatus movement and stops when the apparatus stops.
(b) For testing where the pedestrian test mannequin is stationary, the pedestrian test mannequin faces away from the subject vehicle, and the pedestrian test mannequin legs remain still.
S8.2. Headway calculation. For each test run conducted under S8.3, S8.4, and S8.5, the headway ( L 0 ), in meters, providing 4.0 seconds time to collision ( TTC ) is calculated. L 0 is determined with the following equation where V SV is the speed of the subject vehicle in m/s and V P-y is the component of speed of the pedestrian test mannequin in m/s in the direction of the intended travel path:
S8.3. Pedestrian crossing road.
S8.3.1. Test parameters and setup (unobstructed from right).
(a) The testing area is set up in accordance with figure 3 to this section.
(b) Testing is conducted in the daylight or darkness conditions, except that testing with the pedestrian at the 25 percent overlap is only conducted in daylight conditions.
(c) Testing is conducted using the adult pedestrian test mannequin.
(d) The movement of the pedestrian test mannequin is perpendicular to the subject vehicle's intended travel path.
(e) The pedestrian test mannequin is set up 4.0 ± 0.1 m to the right of the intended travel path.
(f) The intended overlap is 25 percent from the right or 50 percent.
(g) The subject vehicle test speed is any speed between 10 km/h and 60 km/h.
(h) The pedestrian test mannequin speed is 5 km/h.
S8.3.2 Test parameters and setup (unobstructed from left).
(a) The testing area is set up in accordance with figure 4 to this section.
(b) Testing is conducted in the daylight condition.
(c) Testing is conducted using the adult pedestrian mannequin.
(d) The movement of the pedestrian test mannequin is perpendicular to the intended travel path.
(e) The pedestrian test mannequin is set up 6.0 ± 0.1 m to the left of the intended travel path.
(f) The intended overlap is 50 percent.
(g) The subject vehicle test speed is any speed between 10 km/h and 60 km/h.
(h) The pedestrian test mannequin speed is 8 km/h.
S8.3.3. Test parameters and setup (obstructed).
(a) The testing area is set up in accordance with figure 5 to this section.
(b) Testing is conducted in the daylight condition.
(c) Testing is conducted using the child pedestrian test mannequin.
(d) The movement of the pedestrian test mannequin is perpendicular to the intended travel path.
(e) The pedestrian test mannequin is set up 4.0 ± 0.1 m to the right of the intended travel path.
(f) The intended overlap is 50 percent.
(g) Two vehicle test devices are secured in stationary positions parallel to the intended travel path. The two vehicle test devices face the same direction as the intended travel path. One vehicle test device is directly behind the other separated by 1.0 ± 0.1 m. The frontmost plane of the vehicle test device furthermost from the subject vehicle is located 1.0 ± 0.1 m from the parallel contact plane (to the subject vehicle's frontmost plane) on the pedestrian test mannequin. The left side of each vehicle test device is no less than 2.2 m to the right of the vertical plane through the intended travel path. The left side of each vehicle test device is no less than 1.15 m to the right of the vertical plane parallel to the plane through the intended travel path tangent to the 0 percent overlap point.
(h) The subject vehicle test speed is any speed between 10 km/h and 50 km/h.
(i) The pedestrian test mannequin speed is 5 km/h.
S8.3.4. Test conduct prior to forward collision warning or subject vehicle braking onset.
(a) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(b) The subject vehicle approaches the crossing path of the pedestrian test mannequin.
(c) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering inputs such that the subject vehicle's travel path does not deviate more than 0.3 m laterally from the intended travel path, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s prior to any automated braking onset.
(e) The pedestrian test mannequin apparatus is triggered at a time such that the pedestrian test mannequin meets the intended overlap, subject to the criteria in S8.1.2. The pedestrian test mannequin achieves its intended speed within 1.5 m after the apparatus begins to move and maintains its intended speed within 0.4 km/h until the test completion criteria of S8.3.6 are satisfied.
S8.3.5. Test conduct after either forward collision warning or subject vehicle braking onset.
(a) After forward collision warning or subject vehicle braking onset, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles with cruise control active.
(b) No manual brake application is made until the test completion criteria of S8.3.6 are satisfied.
(c) The pedestrian mannequin continues to move until the completion criteria of S8.3.6 are satisfied.
S8.3.6. Test completion criteria. The test run is complete when the subject vehicle comes to a complete stop without making contact with the pedestrian test mannequin, when the pedestrian test mannequin is no longer in the path of the subject vehicle, or when the subject vehicle makes contact with the pedestrian test mannequin.
S8.4. Stationary pedestrian.
S8.4.1. Test parameters and setup.
(a) The testing area is set up in accordance with figure 6 to this section.
(b) Testing is conducted in the daylight or darkness conditions.
(c) Testing is conducted using the adult pedestrian test mannequin.
(d) The pedestrian mannequin is set up at the 25 percent right overlap position facing away from the approaching vehicle.
(e) The subject vehicle test speed is any speed between 10 km/h and 55 km/h.
(f) The pedestrian mannequin is stationary.
S8.4.2. Test conduct prior to forward collision warning or subject vehicle braking onset.
(a) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(b) The subject vehicle approaches the pedestrian test mannequin.
(c) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering inputs such that the subject vehicle's travel path does not deviate more than 0.3 m laterally from the intended travel path, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s prior to any automated braking onset.
S8.4.3. Test conduct after either forward collision warning or subject vehicle braking onset.
(a) After forward collision warning or subject vehicle braking onset, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted with vehicles with cruise control active.
(b) No manual brake application is made until the test completion criteria of S8.4.4 are satisfied.
S8.4.4. Test completion criteria. The test run is complete when the subject vehicle comes to a complete stop without making contact with the pedestrian test mannequin, or when the subject vehicle makes contact with the pedestrian test mannequin.
S8.5. Pedestrian moving along the path.
S8.5.1. Test parameters and setup.
(a) The testing area is set up in accordance with figure 7 to this section.
(b) Testing is conducted in the daylight or darkness conditions.
(c) Testing is conducted using the adult pedestrian test mannequin.
(d) The movement of the pedestrian test mannequin is parallel to and in the same direction as the subject vehicle.
(e) The pedestrian test mannequin is set up in the 25 percent right offset position.
(f) The subject vehicle test speed is any speed between 10 km/h and 65 km/h.
(g) The pedestrian test mannequin speed is 5 km/h.
S8.5.2. Test conduct prior to forward collision warning or subject vehicle braking onset.
(a) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(b) The subject vehicle approaches the pedestrian test mannequin.
(c) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering inputs such that the travel path does not deviate more than 0.3 m laterally from the intended travel path, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s prior to any automated braking onset.
(e) The pedestrian test mannequin apparatus is triggered any time after the distance between the front plane of the subject vehicle and a parallel contact plane on the pedestrian test mannequin corresponds to L 0 . The pedestrian test mannequin achieves its intended speed within 1.5 m after the apparatus begins to move and maintains its intended speed within 0.4 km/h until the test completion criteria of S8.5.4 are satisfied.
S8.5.3. Test conduct after either forward collision warning or subject vehicle braking onset.
(a) After forward collision warning or subject vehicle braking onset, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles with cruise control active.
(b) No manual brake application is made until the test completion criteria of S8.5.4 are satisfied.
S8.5.4. Test completion criteria. The test run is complete when the subject vehicle slows to speed below the pedestrian test mannequin travel speed without making contact with the pedestrian test mannequin or when the subject vehicle makes contact with the pedestrian test mannequin.
S9. False AEB activation.
S9.1. Headway calculation. For each test run to be conducted under S9.2 and S9.3, the headway ( L 0, L 2.1, L 1.1 ), in meters, providing 5.0 seconds, 2.1 seconds, and 1.1 seconds time to collision (TTC) is calculated. L 0 , L 2.1 , and L 1.1 are determined with the following equation where V SV is the speed of the subject vehicle in m/s:
S9.2. Steel trench plate.
S9.2.1. Test parameters and setup.
(a) The testing area is set up in accordance with figure 8 to this section.
(b) The steel trench plate is secured flat on the test surface so that its longest side is parallel to the vehicle's intended travel path and horizontally centered on the vehicle's intended travel path.
(c) The subject vehicle test speed is 80 km/h.
(d) Testing is conducted with manual brake application and without manual brake application.
(e) Testing is conducted during daylight.
S9.2.2. Test conduct.
(a) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(b) The subject vehicle approaches the steel trench plate.
(c) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h of the test speed with minimal and smooth accelerator pedal inputs.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering input such that the travel path does not deviate more than 0.3 m laterally from the intended travel path, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s.
(e) If forward collision warning occurs, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms. This action is omitted for vehicles with cruise control active.
(f) For tests where no manual brake application occurs, manual braking is not applied until the test completion criteria of S9.2.3 are satisfied.
(g) For tests where manual brake application occurs, the subject vehicle's accelerator pedal, if not already released, is released when the headway corresponds to L 2.1 at any rate such that it is fully released within 500 ms.
(h) For tests where manual brake application occurs, the service brakes are applied as specified in S10. The brake application pedal onset occurs at headway L 1.1 .
S9.2.3. Test completion criteria. The test run is complete when the subject vehicle comes to a stop prior to crossing over the leading edge of the steel trench plate or when the subject vehicle crosses over the leading edge of the steel trench plate.
S9.3. Pass-through.
S9.3.1. Test parameters and setup.
(a) The testing area is set up in accordance with figure 9 to this section.
(b) Two vehicle test devices are secured in a stationary position parallel to one another with a lateral distance of 4.5 m ±0.1 m between the vehicles' closest front wheels. The centerline between the two vehicles is parallel to the intended travel path.
(c) The subject vehicle test speed is 80 km/h.
(d) Testing is conducted with manual brake application and without manual brake application.
(e) Testing is conducted during daylight.
S9.3.2. Test conduct.
(a) Before the headway corresponds to L 0 , the subject vehicle is driven at any speed, in any direction, on any road surface, for any amount of time.
(b) The subject vehicle approaches the gap between the two vehicle test devices.
(c) Beginning when the headway corresponds to L 0 , the subject vehicle speed is maintained within 1.6 km/h with minimal and smooth accelerator pedal inputs.
(d) Beginning when the headway corresponds to L 0 , the subject vehicle heading is maintained with minimal steering input such that the travel path does not deviate more than 0.3 m laterally from the intended travel path, and the yaw rate of the subject vehicle does not exceed ±1.0 deg/s.
(e) If forward collision warning occurs, the subject vehicle's accelerator pedal is released at any rate such that it is fully released within 500 ms.
(f) For tests where no manual brake application occurs, manual braking is not applied until the test completion criteria of S9.3.3 are satisfied.
(g) For tests where manual brake application occurs, the subject vehicle's accelerator pedal, if not already released, is released when the headway corresponds to L 2.1 at any rate such that it is fully released within 500 ms.
(h) For tests where manual brake application occurs, the service brakes are applied as specified in S10. The brake application onset occurs when the headway corresponds to L 1.1 .
S9.3.3. Test completion criteria. The test run is complete when the subject vehicle comes to a stop prior to its rearmost point passing the vertical plane connecting the forwardmost point of the vehicle test devices or when the rearmost point of the subject vehicle passes the vertical plane connecting the forwardmost point of the vehicle test devices.
S10. Subject vehicle brake application procedure.
S10.1. The procedure begins with the subject vehicle brake pedal in its natural resting position with no preload or position offset.
S10.2. At the option of the manufacturer, either displacement feedback, hybrid feedback, or force feedback control is used.
S10.3. Displacement feedback procedure. For displacement feedback, the commanded brake pedal position is the brake pedal position that results in a mean deceleration of 0.4 g in the absence of AEB system activation.
(a) The mean deceleration is the deceleration over the time from the brake pedal achieving the commanded position to 250 ms before the vehicle comes to a stop.
(b) The pedal displacement controller displaces the brake pedal at a rate of 254 mm/s ±25.4 mm/s to the commanded brake pedal position.
(c) The pedal displacement controller may overshoot the commanded position by any amount up to 20 percent. If such an overshoot occurs, it is corrected within 250 ms from when the commanded position is first achieved.
(d) The achieved brake pedal position is any position within 10 percent of the commanded position from 250 ms after the commanded brake pedal position is first achieved to the end of the test.
S10.4. Hybrid brake pedal feedback procedure. For hybrid brake pedal feedback, the commanded brake pedal application is the brake pedal position and a subsequent commanded brake pedal force that results in a mean deceleration of 0.4 g in the absence of AEB system activation.
(a) The mean deceleration is the deceleration over the time from the brake pedal achieving the commanded position to 250 ms before the vehicle comes to a stop.
(b) The hybrid controller displaces the brake pedal at a rate of 254 mm/s ±25.4 mm/s to the commanded pedal position.
(c) The hybrid controller may overshoot the commanded position by any amount up to 20 percent. If such an overshoot occurs, it is corrected within 250 ms from then the commanded position is first achieved.
(d) The hybrid controller begins to control the force applied to the brake pedal and stops controlling pedal displacement within 100 ms after the commanded brake pedal displacement occurs.
(e) The hybrid controller applies a pedal force of at least 11.1 N from the onset of the brake application until the end of the test.
(f) The average pedal force is maintained within 10 percent of the commanded brake pedal force from 350 ms after commended pedal displacement occurs until test completion.
S10.5. Force feedback procedure. For force feedback, the commanded brake pedal application is the brake pedal force that results in a mean deceleration of 0.4 g in the absence of AEB system activation.
(a) The mean deceleration is the deceleration over the time from when the commanded brake pedal force is first achieved to 250 ms before the vehicle comes to a stop.
(b) The force controller achieves the commanded brake pedal force within 250 ms. The application rate is unrestricted.
(c) The force controller may overshoot the commanded force by any amount up to 20 percent. If such an overshoot occurs, it is corrected within 250 ms from when the commanded force is first achieved.
(d) The force controller applies a pedal force of at least 11.1 N from the onset of the brake application until the end of the test.
(e) The average pedal force is maintained within 10 percent of the commanded brake pedal force from 250 ms after commended pedal force occurs until test completion.
§ 571.128   [Reserved]
§ 571.129   Standard No. 129; New non-pneumatic tires for passenger cars.
S1 Scope. This standard specifies tire dimensions and laboratory test requirements for lateral strength, strength, endurance, and high speed performance; defines the tire load rating; and specifies labeling requirements for non-pneumatic spare tires.
S2 Application. This standard applies to new temporary spare non-pneumatic tires for use on passenger cars.
S3 Definitions.
Carcass means the tire structure except for the tread which provides the major portion of the tire's capability to deflect in response to the vertical loads and tractive forces that the tire transmits from the roadway to the non-pneumatic rim, the wheel center member, or the vehicle and which attaches to the vehicle or attaches, either integrally or separably, to the wheel center member or non-pneumatic rim.
Carcass separation means the pulling away of the carcass from the non-pneumatic rim or wheel center member.
Chunking means the breaking away of pieces of the carcass or tread.
Cracking means any parting within the carcass, tread, or any components that connect the tire to the non-pneumatic rim or wheel center member and, if the non-pneumatic tire is integral with the non-pneumatic rim or wheel center member, any parting within the non-pneumatic rim, or wheel center member.
Load rating means the maximum load a tire is rated to carry.
Maximum tire width means the greater of either the linear distance between the exterior edges of the carcass or the linear distance between the exterior edges of the tread, both being measured parallel to the rolling axis of the tire.
Non-pneumatic rim means a mechanical device which, when a non-pneumatic tire assembly incorporates a wheel, supports the tire, and attaches, either integrally or separably, to the wheel center member and upon which the tire is attached.
Non-pneumatic test rim means with reference to a tire to be tested, any non-pneumatic rim that is listed as appropriate for use with that tire in accordance with S4.4.
Non-pneumatic tire means a mechanical device which transmits, either directly or through a wheel or wheel center member, the vertical load and tractive forces from the roadway to the vehicle, generates the tractive forces that provide the directional control of the vehicle and does not rely on the containment of any gas or fluid for providing those functions.
Non-pneumatic tire assembly means a non-pneumatic tire, alone or in combination with a wheel or wheel center member, which can be mounted on a vehicle.
Non-pneumatic tire identification code means an alphanumeric code that is assigned by the manufacturer to identify the tire with regard to its size, application to a specific non-pneumatic rim or wheel center member or application to a specific vehicle.
Test wheel center member means with reference to a tire to be tested, any wheel center member that is listed as appropriate for use with that tire in accordance with S4.4.
Tread means that portion of the tire that comes in contact with the road.
Tread separation means pulling away of the tread from the carcass.
Wheel means a mechanical device which consists of a non-pneumatic rim and wheel center member and which, in the case of a non-pneumatic tire assembly incorporating a wheel, provides the connection between the tire and the vehicle.
Wheel center member means, in the case of a non-pneumatic tire assembly incorporating a wheel, a mechanical device which attaches, either integrally or separably, to the non-pneumatic rim and provides the connection between the non-pneumatic rim and the vehicle; or in the case of a non-pneumatic tire assembly not incorporating a wheel, a mechanical device which attaches, either integrally or separably, to the non-pneumatic tire and provides the connection between the tire and the vehicle.
S4 Requirements.
S4.1 Size and Construction. Each tire shall be designed to fit each non-pneumatic rim or wheel center member specified for its non-pneumatic tire identification code designation in a listing in accordance with section S4.4.
S4.2 Performance Requirements
S4.2.1 General. Each tire shall conform to the following:
(a) Its load rating shall be that specified in a submission made by a manufacturer, pursuant to S4.4(a), or in one of the publications described in S4.4(b) for its non-pneumatic tire identification code designation.
(b) It shall incorporate a tread wear indicator that will provide a visual indication that the tire has worn to a tread depth of 1/16 inch.
(c) It shall, before being subjected to either the endurance test procedure specified in S5.4 or the high speed performance procedure specified in S5.5, exhibit no visual evidence of tread or carcass separation, chunking or cracking.
(d) It shall meet the requirements of S4.2.2.5 and S4.2.2.6 when tested on a test wheel described in S5.4.2.1 either alone or simultaneously with up to 5 tires.
S4.2.2 Test Requirements.
S.4.2.2.1 Test Sample. For each test sample use:
(a) One tire for physical dimensions, lateral strength, and strength in sequence;
(b) A second tire for tire endurance; and
(c) A third tire for high speed performance.
S4.2.2.2 Physical Dimensions. For a non-pneumatic tire assembly in which the tire is separable from the non-pneumatic rim or wheel center member, the dimensions, measured in accordance with S5.1, for that portion of the tire that attaches to that non-pneumatic rim or wheel center member shall satisfy the dimensional specifications contained in the submission made by an individual manufacturer, pursuant to S4.4(a), or in one of the publications described in S4.4(b) for that tire's non-pneumatic tire identification code designation.
S4.2.2.3 Lateral Strength. There shall be no visual evidence of tread or carcass separation, cracking or chunking, when a tire is tested in accordance with S5.2 to a load of:
(a) 1,500 pounds for tires with a load rating less than 880 pounds;
(b) 2,000 pounds for tires with a load rating of 880 pounds or more but less than 1,400 pounds.
(c) 2,500 pounds for tires with a load rating of 1,400 pounds or more, using the load rating marked on the tire or tire assembly.
S4.2.2.4 Tire Strength. There shall be no visual evidence of tread carcass separation, cracking or chunking, when a tire is tested in accordance with S5.3 to a minimum energy level of:
S4.2.2.5 Tire Endurance. When the tire has been subjected to the laboratory endurance test specified in S5.4, using, if applicable, a non-pneumatic test rim or test wheel center member that undergoes no permanent deformation, there shall be no visual evidence of tread or carcass separation, cracking or chunking. In the case of a non-pneumatic tire assembly in which the non-pneumatic tire is an integral part of the assembly, the assembly shall undergo no permanent deformation with the exception of wear of the tread.
S4.2.2.6 High Speed Performance. When the tire has been subjected to the laboratory high speed performance test specified in S5.5, using if applicable, a non-pneumatic test rim or test wheel center member that undergoes no permanent deformation, there shall be no visual evidence of tread or carcass separation, cracking or chunking. In the case of a non-pneumatic tire assembly in which the non-pneumatic tire is an integral part of the assembly, the assembly shall undergo no permanent deformation with the exception of wear of the tread.
S4.3 Labeling requirements. Each new non-pneumatic tire shall comply, according to the phase-in schedule specified in S7 of this standard, with the requirements of S5.5 and S5.5.1 of § 571.139.
S4.4 Non-Pneumatic Tire Identification Code and Non-Pneumatic Rim/Wheel Center Member Matching Information. For purposes of this standard, S8 of 49 CFR 571.110 and S10 of 49 CFR 571.120, each manufacturer of a non-pneumatic tire that is not an integral part of a non-pneumatic tire assembly shall ensure that it provides a listing to the public for each non-pneumatic tire that it produces. The listing shall include the non-pneumatic tire identification code, tire load rating, dimensional specifications and a diagram of the portion of the tire that attaches to the non-pneumatic rim or wheel center member, and a list of the non-pneumatic rims or wheel center members that may be used with that tire. For each non-pneumatic rim or wheel center member included in such a listing, the information provided shall include a size and type designation for the non-pneumatic rim or wheel center member, and dimensional specifications and a diagram of the non-pneumatic rim or portion of the wheel center member that attaches to the tire. A listing compiled in accordance with paragraph (a) of this section need not include dimensional specifications or a diagram of the non-pneumatic rim or portion of the wheel center member that attaches to the tire if the non-pneumatic rim's or portion of the wheel center member's dimensional specifications and diagram are contained in each listing published in accordance with paragraph (b) of this section. The listing shall be in one of the following forms:
(a) Listed by manufacturer name or brand name in a document furnished to dealers of the manufacturer's tires or, in the case of non-pneumatic tires supplied only as a temporary spare tire on a vehicle, in a document furnished to dealers of vehicles equipped with the tires, to any person upon request, and in duplicate to the Office of Vehicle Safety Standards, Crash Avoidance Division, National Highway Traffic Safety Administration, U.S. Department of Transportation, Washington, DC 20590; or
(b) Contained in publications, current at the date of manufacture of the tire or any later date, of at least one of the following organizations:
S5. Test Procedures.
S5.1 Physical Dimensions. After conditioning the tire at room temperature for at least 24 hours, using equipment with minimum measurement capabilities of one-half the smallest tolerance specified in the listing contained in the submission made by a manufacturer pursuant to S4.4(a), or in one of the publications described in S4.4(b) for that tire's non-pneumatic tire identification code designation, measure the portion of the tire that attaches to the non-pneumatic rim or the wheel center member. For any inner diameter dimensional specifications, or other dimensional specifications that are uniform or uniformly spaced around some circumference of the tire, these measurements shall be taken at least six points around the tire, or, if specified, at the points specified in the listing contained in the submission made by an individual manufacturer, pursuant to S4.4(a), or in one of the publications described in S4.4(b) for that tire's non-pneumatic tire identification code designation.
S5.2 Lateral Strength.
S5.2.1 Preparation of the tire.
S5.2.1.1 If applicable, mount a new tire on a non-pneumatic test rim or test wheel center member.
S5.2.1.2 Mount the tire assembly in a fixture as shown in Figure 1 with the surface of the tire assembly that would face outward when mounted on a vehicle facing toward the lateral strength test block shown in Figure 2 and force the lateral strength test block against the tire.
S5.2.2 Test Procedure.
S5.2.2.1 Apply a load through the block to the tire at a rate of 2 inches per minute, with the load arm parallel to the tire assembly at the time of engagement and the first point of contact with the test block being the test block centerline shown in Figure 2, at the following distances, B, in sequence, as shown in Figure 1:
S5.3 Tire Strength.
S5.3.1 Preparation of the Tire.
S5.3.1.1 If applicable, mount the tire on a non-pneumatic test rim or test wheel center member.
S5.3.1.2 Condition the tire assembly at room temperature for at least three hours.
S5.3.2 Test Procedures.
S5.3.2.1 Force the test cleat, as defined in S5.3.2.2, with its length axis (see S5.3.2.2(a)) parallel to the rolling axis of the non-pneumatic tire assembly, and its height axis (see S5.3.2.2(c)), coinciding with a radius of the non-pneumatic tire assembly, into the tread of the tire at five test points equally spaced around the circumference of the tire. At each test point, the test cleat is forced into the tire at a rate of two inches per minute until the applicable minimum energy level, as shown in S4.2.2.4, calculated using the formula contained in S5.3.2.3, is reached.
S5.3.2.2 The test cleat is made of steel and has the following dimensions;
(a) Minimum length of one inch greater than the maximum tire width of the tire,
(b) Width of one-half inch with the surface which contacts the tire's tread having one-quarter inch radius, and
(c) Minimum height of one inch greater than the difference between the unloaded radius of the non-pneumatic tire assembly and the maximum radius of the non-pneumatic rim or wheel center member, if used with the non-pneumatic tire assembly being tested.
S5.3.2.3 The energy level is calculated by the following formula:
S5.4 Tire Endurance.
S5.4.1 Preparation of the tire.
S5.4.1.1 If applicable, mount a new tire on a non-pneumatic test rim or test wheel center member.
S5.4.1.2 Condition the tire assembly to 100 ±5 °F. for at least three hours.
S5.4.2 Test Procedure.
S5.4.2.1 Mount the tire assembly on a test axle and press it against a flat-faced steel test wheel 67.23 inches in diameter and at least as wide as the maximum tire width of the tire to be tested or an approved equivalent test wheel, with the applicable test load specified in the table in S5.4.2.3 for the tire's non-pneumatic tire identification code designation.
S5.4.2.2 During the test, the air surrounding the test area shall be 100 ±5 °F.
S5.4.2.3 Conduct the test at 50 miles per hour (m.p.h.) in accordance with the following schedule without interruption: The loads for the following periods are the specified percentage of the load rating marked on the tire or tire assembly:
S5.4.2.4 Immediately after running the tire the required time, allow the tire to cool for one hour, then, if applicable, detach it from the non-pneumatic test rim or test wheel center member, and inspect it for the conditions specified in S4.2.2.5.
S5.5 High Speed Endurance.
S5.5.1 After preparing the tire in accordance with S5.4.1, if applicable, mount the tire assembly in accordance with S5.4.2.1, and press it against the test wheel with a load of 88 percent of the tire's load rating as marked on the tire or tire assembly.
S5.5.2 Break in the tire by running it for 2 hours at 50 m.p.h.
S5.5.3 Allow to cool to 100 ±5 °F.
S5.5.4 Test at 75 m.p.h. for 30 minutes, 80 m.p.h. for 30 minutes and 85 m.p.h. for 30 minutes.
S5.5.5 Immediately after running the tire for the required time, allow the tire to cool for one hour, then, if applicable, detach it from the non-pneumatic test rim or test wheel center member, and inspect it for the conditions specified in S4.2.2.6.
S6. Nonconforming tires. Any non-pneumatic tire that is designed for use on passenger cars that does not conform to all the requirements of this standard, shall not be sold, offered for sale, introduced or delivered for introduction into interstate commerce, or imported into the United States, for any purpose.
S7 Phase-In Schedule for labeling requirements.
S7.1 Tires manufactured on or after September 1, 2005 and before September 1, 2006. For tires manufactured on or after September 1, 2005 and before September 1, 2006, the number of tires complying with S4.3 of this standard must be equal to not less than 40% of the manufacturer's production during that period.
S7.2 Tires manufactured on or after September 1, 2006 and before September 1, 2007. For tires manufactured on or after September 1, 2006 and before September 1, 2007, the number of tires complying with S4.3 of this standard must be equal to not less than 70% of the manufacturer's production during that period.
S7.3 Tires manufactured on or after September 1, 2007. Each tire must comply with S6.3 of this standard.
§ 571.131   Standard No. 131; School bus pedestrian safety devices.
S1. Scope. This standard establishes requirements for devices that can be installed on school buses to improve the safety of pedestrians in the vicinity of stopped school buses.
S2. Purpose. The purpose of this standard is to reduce deaths and injuries by minimizing the likelihood of vehicles passing a stopped school bus and striking pedestrians in the vicinity of the bus.
S3. Application. This standard applies to school buses other than multifunction school activity buses.
S4. Definitions.
Stop signal arm means a device that can be extended outward from the side of a school bus to provide a signal to other motorists not to pass the bus because it has stopped to load or discharge passengers.
S5. Requirements. Each school bus shall be equipped with a stop signal arm meeting the requirements of S5.1 through S5.5 as depicted in Figure 1.
S5.1 The stop signal arm shall be a regular octagon which is at least 450 mm × 450 mm (17.72 inches × 17.72 inches) in diameter.
S5.2 The stop signal arm shall be red on both sides, except as provided in S5.2.1 and S5.2.2, and S5.2.3.
S5.2.1 The stop signal arm shall have a white border at least 12 mm (0.47 inches) wide on both sides, except as provided in S5.2.3. Mounting brackets, clips, bolts, or other components necessary to the mechanical or electrical operation of the stop signal arm may not obscure more than 15 percent of the border on each side of the stop arm. The portion of the border that may be obscured is in addition to that portion which may be obscured by the two red lamps specified in S5.3.2.
S.5.2.2 The stop signal arm shall have the word “STOP” displayed in white upper-case letters on both sides, except as provided in S5.2.3. The letters shall be at least 150 mm (5.9 inches) in height. The letters shall have a stroke width of at least 20 mm (0.79 inches), except as provided in S.5.3.1.1.
S5.2.3 When two stop signal arms are installed on a school bus, the rearmost stop signal arm shall not contain any lettering, symbols, or markings on the forward side.
S5.3 Conspicuity. The stop signal arm shall comply with either S5.3.1 or S5.3.2, or both.
S5.3.1 Except as provided in S5.3.1.1, S5.3.1.2, or S5.3.1.3, the entire surface of both sides of each stop signal arm shall be reflectorized with Type III retroreflectorized material that meets the minimum specific intensity requirements of S6.1 and Table I.
S.5.3.1.1 The legend of the retroreflective stop arm may be illuminated in a manner such that light is emitted from the surface of each letter or from the area immediately surrounding each letter. Only red lamps may be used. They shall form the complete shape of each letter of the legend, and shall be affixed to all letters (or to the areas immediately surrounding all letters) in the legend. The shape of each letter shall remain constant and, if the lamps are contained within each letter, the net stroke width (stroke width minus the width of the lamp(s)) of each letter of the legend, specified in S5.2.2, shall not be less than 15 mm (0.59 inch). When the stop arm is extended, the lamps shall flash at the rate specified in S6.2.2, with a current “on” time specified in S6.2.2.1. All lamps shall be positioned in one of the two following ways:
(1) centered within the stroke of each letter of the legend, or
(2) outlining each letter of the legend.
S5.3.1.2 Nonreflectorized mounting brackets, clips, bolts, or other components necessary to the mechanical or electrical operation of the stop signal arm shall not obscure more than 7.5 percent of the total surface area of either side of the stop signal arm.
S5.3.1.3 When two stop signal arms are installed on a school bus, the forward side of the rearmost stop signal arm shall not be reflectorized.
S5.3.2 Each side of the stop signal arm shall have at least two red lamps that meet the requirements of S6.2. The lamps shall be centered on the vertical centerline of the stop arm. One of the lamps shall be located at the extreme top of the stop arm and the other at its extreme bottom.
S5.4 The stop signal arm shall be installed on the left side of the bus.
S5.4.1 The stop signal arm shall be located such that, when in the extended position:
(a) The stop signal arm is perpendicular to the side of the bus, plus or minus five degrees;
(b) The top edge of the stop signal arm is parallel to and not more than 6 inches from a horizontal plane tangent to the lower edge of the frame of the passenger window immediately behind the driver's window; and
(c) The vertical centerline of the stop signal arm is not less than 9 inches away from the side of the school bus.
S5.4.2 A second stop signal arm may be installed on a school bus. That stop signal arm shall comply with S5.4 and S5.4.1.
S5.5 The stop signal arm shall be automatically extended in such a manner that it complies with S5.4.1, at a minimum whenever the red signal lamps required by S5.1.4 of Standard No. 108 are activated; except that a device may be installed that prevents the automatic extension of a stop signal arm. The mechanism for activating the device shall be within the reach of the driver. While the device is activated, a continuous or intermittent signal audible to the driver shall sound. The audible signal may be equipped with a timing device requiring the signal to sound for at least 60 seconds. If a timing device is used, it shall automatically recycle every time the service entry door is opened while the engine is running and the manual override is engaged.
S6 Test Procedures.
S6.1 Reflectivity Test. When tested under the conditions specified in S6.2 (b), (c), and (d) of Federal motor vehicle safety standard 125, Warning Devices, (49 CFR 571.125), the retroreflective materials shall meet the criteria specified in table 1.
Table 1—Minimum Specific Intensity per Unit Area (SIA)
(Candelas per Footcandle per Square Foot)
S6.2 Lighting Tests.
S6.2.1 Color. The procedure shall be done in accordance with SAE Recommended Practice J578-1988 (incorporated by reference, see § 571.5). When visually compared to the light emitted from a filter/source with a combination of chromaticity coordinates as explained in SAE Recommended Practice J578-1988 within specific boundaries [y = 0.33 (yellow boundary) and y = 0.98— × (purple boundary)] the color of light emitted from the test object shall not be less saturated (paler), yellower, or purpler. The test object shall be placed perpendicular to the light source to simulate lamps on stop signal arms. In making visual comparisons, the light from the test object shall light one portion of a comparison field and the light from the filter/source standard shall light an adjacent area. To make a valid visual comparison, the two fields to be viewed shall be of near equal luminance.
S6.2.2. Flash rate. The lamps on each side of the stop signal arm, when operated at the manufacturer's design load, shall flash alternately at a rate of 60 to 120 flashes per minute.
S6.2.2.1 Lamps, except those subject to S6.2.2.2, shall have a current “on” time of 30 to 75 percent of the total flash cycle. The total current “on” time for the two terminals shall be between 90 and 110 percent of the total flash cycle.
S6.2.2.2 Xenon short-arc gaseous discharge lamps shall have an “off” time before each flash of at least 50 percent of the total flash cycle.
S6.2.3 Vibration, Moisture, Dust, Corrosion, Photometry, and Warpage Tests. The procedure shall be done in accordance with SAE Recommended Practice J575-1983 (incorporated by reference, see § 571.5) and SAE Recommended Practice J1133 (1984) (incorporated by reference, see § 571.5). Lamps and lighting components shall meet the criteria for vibration, moisture, dust, corrosion, photometry, and warpage in SAE Recommended Practice J575-1983 and SAE Recommended Practice J1133 (1984) under the test conditions specified herein.
§ 571.135   Standard No. 135; Light vehicle brake systems.
S1. Scope. This standard specifies requirements for service brake and associated parking brake systems.
S2. Purpose. The purpose of this standard is to ensure safe braking performance under normal and emergency driving conditions.
S3. Application. This standard applies to passenger cars manufactured on or after September 1, 2000 and to multi-purpose passenger vehicles, trucks and buses with a gross vehicle weight rating (GVWR) of 3,500 kilograms (7,716 pounds) or less, manufactured on or after September 1, 2002. In addition, at the option of the manufacturer, passenger cars manufactured before September 1, 2000, and multi-purpose passenger vehicles, trucks and buses with a GVWR of 3,500 kilograms (7,716 pounds) or less, manufactured before September 1, 2002, may meet the requirements of this standard instead of Federal Motor Vehicle No. 105, Hydraulic Brake Systems.
S4. Definitions.
Adhesion utilization curves means curves showing, for specified load conditions, the adhesion utilized by each axle of a vehicle plotted against the braking ratio of the vehicle.
Antilock brake system or ABS means a portion of a service brake system that automatically controls the degree of rotational wheel slip during braking by:
(1) Sensing the rate of angular rotation of the wheels;
(2) Transmitting signals regarding the rate of wheel angular rotation to one or more controlling devices which interpret those signals and generate responsive controlling output signals; and
(3) Transmitting those controlling signals to one or more modulator devices which adjust brake actuating forces in response to those signals.
Backup system means a portion of a service brake system, such as a pump, that automatically supplies energy in the event of a primary brake power source failure.
Brake factor means the slope of the linear least squares regression equation best representing the measured torque output of a brake as a function of the measured applied line pressure during a given brake application for which no wheel lockup occurs.
Brake hold-off pressure means the maximum applied line pressure for which no brake torque is developed, as predicted by the pressure axis intercept of the linear least squares regression equation best representing the measured torque output of a brake as a function of the measured applied line pressure during a given brake application.
Brake power assist unit means a device installed in a hydraulic brake system that reduces the amount of muscular force that a driver must apply to actuate the system, and that, if inoperative, does not prevent the driver from braking the vehicle by a continued application of muscular force on the service brake control.
Brake power unit means a device installed in a brake system that provides the energy required to actuate the brakes, either directly or indirectly through an auxiliary device, with driver action consisting only of modulating the energy application level.
Braking ratio means the deceleration of the vehicle divided by the gravitational acceleration constant.
Electric vehicle or EV means a motor vehicle that is powered by an electric motor drawing current from rechargeable storage batteries, fuel cells, or other portable sources of electrical current, and which may include a non-electrical source of power designed to charge batteries and components thereof.
Electrically-actuated service brakes means service brakes that utilize electrical energy to actuate the foundation brakes.
Functional failure means a failure of a component (either electrical or mechanical in nature) which renders the system totally or partially inoperative yet the structural integrity of the system is maintained.
Hydraulic brake system means a system that uses hydraulic fluid as a medium for transmitting force from a service brake control to the service brake and that may incorporate a brake power assist unit, or a brake power unit.
Initial brake temperature or IBT means the average temperature of the service brakes on the hottest axle of the vehicle 0.32 km (0.2 miles) before any brake application.
Lightly loaded vehicle weight or LLVW means unloaded vehicle weight plus the weight of a mass of 180 kg (396 pounds), including driver and instrumentation.
Maximum speed of a vehicle or VMax means the highest speed attainable by accelerating at a maximum rate from a standing start for a distance of 3.2 km (2 miles) on a level surface, with the vehicle at its lightly loaded vehicle weight, and, if an EV, with the propulsion batteries at a state of charge of not less than 95 percent at the beginning of the run.
Objective brake factor means the arithmetic average of all the brake factors measured over the twenty brake applications defined in S7.4, for all wheel positions having a given brake configuration.
Peak friction coefficient or PFC means the ratio of the maximum value of braking test wheel longitudinal force to the simultaneous vertical force occurring prior to wheel lockup, as the braking torque is progressively increased.
Pressure component means a brake system component that contains the brake system fluid and controls or senses the fluid pressure.
Regenerative braking system or RBS means an electrical energy system that is installed in an EV for recovering or dissipating kinetic energy, and which uses the propulsion motor(s) as a retarder for partial braking of the EV while returning electrical energy to the propulsion battery(s) or dissipating electrical energy.
Snub means the braking deceleration of a vehicle from a higher reference speed to a lower reference speed that is greater than zero.
Split service brake system means a brake system consisting of two or more subsystems actuated by a single control, designed so that a single failure in any subsystem (such as a leakage-type failure of a pressure component of a hydraulic subsystem except structural failure of a housing that is common to two or more subsystems, or an electrical failure in an electric subsystem) does not impair the operation of any other subsystem.
Stopping distance means the distance traveled by a vehicle from the point of application of force to the brake control to the point at which the vehicle reaches a full stop.
Variable brake proportioning system means a system that has one or more proportioning devices which automatically change the brake pressure ratio between any two or more wheels to compensate for changes in wheel loading due to static load changes and/or dynamic weight transfer, or due to deceleration.
Wheel lockup means 100 percent wheel slip.
S5. Equipment requirements.
S5.1. Service brake system. Each vehicle shall be equipped with a service brake system acting on all wheels.
S5.1.1. Wear adjustment. Wear of the service brakes shall be compensated for by means of a system of automatic adjustment.
S5.1.2. Wear status. The wear condition of all service brakes shall be indicated by either:
(a) Acoustic or optical devices warning the driver at his or her driving position when lining replacement is necessary, or
(b) A means of visually checking the degree of brake lining wear, from the outside or underside of the vehicle, utilizing only the tools or equipment normally supplied with the vehicle. The removal of wheels is permitted for this purpose.
S5.1.3 Regenerative braking system. (a) For an EV equipped with RBS, the RBS is considered to be part of the service brake system if it is automatically activated by an application of the service brake control, if there is no means provided for the driver to disconnect or otherwise deactivate it, and if it is activated in all transmission positions, including neutral.
(b) For an EV that is equipped with both ABS and RBS that is part of the service brake system, the ABS must control the RBS.
S5.2. Parking brake system. Each vehicle shall be equipped with a parking brake system of a friction type with solely mechanical means to retain engagement.
S5.3. Controls.
S5.3.1. The service brakes shall be activated by means of a foot control. The control of the parking brake shall be independent of the service brake control, and may be either a hand or foot control.
S5.3.2. For vehicles equipped with ABS, a control to manually disable the ABS, either fully or partially, is prohibited.
S5.4. Reservoirs.
S5.4.1. Master cylinder reservoirs. A master cylinder shall have a reservoir compartment for each service brake subsystem serviced by the master cylinder. Loss of fluid from one compartment shall not result in a complete loss of brake fluid from another compartment.
S5.4.2. Reservoir capacity. Reservoirs, whether for master cylinders or other type systems, shall have a total minimum capacity equivalent to the fluid displacement resulting when all the wheel cylinders or caliper pistons serviced by the reservoirs move from a new lining, fully retracted position (as adjusted initially to the manufacturer's recommended setting) to a fully worn, fully applied position, as determined in accordance with S7.17(c) of this standard. Reservoirs shall have completely separate compartments for each subsystem except that in reservoir systems utilizing a portion of the reservoir for a common supply to two or more subsystems, individual partial compartments shall each have a minimum volume of fluid equal to at least the volume displaced by the master cylinder piston servicing the subsystem, during a full stroke of the piston. Each brake power unit reservoir servicing only the brake system shall have a minimum capacity equivalent to the fluid displacement required to charge the system piston(s) or accumulator(s) to normal operating pressure plus the displacement resulting when all the wheel cylinders or caliper pistons serviced by the reservoir or accumulator(s) move from a new lining, fully retracted position (as adjusted initially to the manufacturer's recommended setting) to a fully worn, fully applied position.
S5.4.3. Reservoir labeling. Each vehicle equipped with hydraulic brakes shall have a brake fluid warning statement that reads as follows, in letters at least 3.2 mm ( 1/8 inch) high: “WARNING: Clean filler cap before removing. Use only ______ fluid from a sealed container.” (Inserting the recommended type of brake fluid as specified in 49 CFR 571.116, e.g., “DOT 3.”) The lettering shall be:
(a) Permanently affixed, engraved or embossed;
(b) Located so as to be visible by direct view, either on or within 100 mm (3.94 inches) of the brake fluid reservoir filler plug or cap; and
(c) Of a color that contrasts with its background, if it is not engraved or embossed.
S5.4.4. Fluid level indication. Brake fluid reservoirs shall be so constructed that the level of fluid can be checked without need for the reservoir to be opened. This requirement is deemed to have been met if the vehicle is equipped with a transparent brake fluid reservoir or a brake fluid level indicator meeting the requirements of S5.5.1(a)(1).
S5.5. Brake system warning indicator. Each vehicle shall have one or more visual brake system warning indicators, mounted in front of and in clear view of the driver, which meet the requirements of S5.5.1 through S5.5.5. In addition, a vehicle manufactured without a split service brake system shall be equipped with an audible warning signal that activates under the conditions specified in S5.5.1(a).
S5.5.1. Activation. An indicator shall be activated when the ignition (start) switch is in the “on” (“run”) position and whenever any of conditions (a) through (g) occur:
(a) A gross loss of fluid or fluid pressure (such as caused by rupture of a brake line but not by a structural failure of a housing that is common to two or more subsystems) as indicated by one of the following conditions (chosen at the option of the manufacturer):
(1) A drop in the level of the brake fluid in any master cylinder reservoir compartment to less than the recommended safe level specified by the manufacturer or to one-fourth of the fluid capacity of that reservoir compartment, whichever is greater.
(2) For vehicles equipped with a split service brake system, a differential pressure of 1.5 MPa (218 psi) between the intact and failed brake subsystems measured at a master cylinder outlet or a slave cylinder outlet.
(3) A drop in the supply pressure in a brake power unit to one-half of the normal system pressure.
(b) Any electrical functional failure in an antilock or variable brake proportioning system.
(c) Application of the parking brake.
(d) Brake lining wear-out, if the manufacturer has elected to use an electrical device to provide an optical warning to meet the requirements of S5.1.2(a).
(e) For a vehicle with electrically-actuated service brakes, failure of the source of electric power to those brakes, or diminution of state of charge of the batteries to less than a level specified by the manufacturer for the purpose of warning a driver of degraded brake performance.
(f) For a vehicle with electric transmission of the service brake control signal, failure of a brake control circuit.
(g) For an EV with a regenerative braking system that is part of the service brake system, failure of the RBS.
S5.5.2. Function check. (a) All indicators shall be activated as a check function by either:
(1) Automatic activation when the ignition (start) switch is turned to the “on” (“run”) position when the engine is not running, or when the ignition (“start”) switch is in a position between “on” (“run”) and “start” that is designated by the manufacturer as a check position, or
(2) A single manual action by the driver, such as momentary activation of a test button or switch mounted on the instrument panel in front of and in clear view of the driver, or, in the case of an indicator for application of the parking brake, by applying the parking brake when the ignition is in the “on” (“run”) position.
(b) In the case of a vehicle that has an interlock device that prevents the engine from being started under one or more conditions, check functions meeting the requirements of S5.5.2(a) need not be operational under any condition in which the engine cannot be started.
(c) The manufacturer shall explain the brake check function test procedure in the owner's manual.
S5.5.3. Duration. Each indicator activated due to a condition specified in S5.5.1 shall remain activated as long as the condition exists, whenever the ignition (“start”) switch is in the “on” (“run”) position, whether or not the engine is running.
S5.5.4. Function. When a visual warning indicator is activated, it may be continuous or flashing, except that the visual warning indicator on a vehicle not equipped with a split service brake system shall be flashing. The audible warning required for a vehicle manufactured without a split service brake system may be continuous or intermittent.
S5.5.5. Labeling. (a) Each visual indicator shall display a word or words in accordance with the requirements of Standard No. 101 (49 CFR 571.101) and this section, which shall be legible to the driver under all daytime and nighttime conditions when activated. Unless otherwise specified, the words shall have letters not less than 3.2 mm ( 1/8 inch) high and the letters and background shall be of contrasting colors, one of which is red. Words or symbols in addition to those required by Standard No. 101 and this section may be provided for purposes of clarity.
(b) Vehicles manufactured with a split service brake system may use a common brake warning indicator to indicate two or more of the functions described in S5.5.1(a) through S5.5.1(g). If a common indicator is used, it shall display the word “Brake.”
(c) A vehicle manufactured without a split service brake system shall use a separate indicator to indicate the failure condition in S5.5.1(a). This indicator shall display the words “STOP—BRAKE FAILURE” in block capital letters not less than 6.4 mm ( 1/4 inch) in height.
(d) If separate indicators are used for one or more of the conditions described in S5.5.1(a) through S5.5.1(g), the indicators shall display the following wording:
(1) If a separate indicator is provided for the low brake fluid condition in S5.5.1(a)(1), the words “Brake Fluid” shall be used except for vehicles using hydraulic system mineral oil.
(2) If a separate indicator is provided for the gross loss of pressure condition in S5.5.1(a)(2), the words “Brake Pressure” shall be used.
(3) If a separate indicator is provided for the condition specified in S5.5.1(b), the letters and background shall be of contrasting colors, one of which is yellow. The indicator shall be labeled with the words “Antilock” or “Anti-lock” or “ABS”; or “Brake Proportioning,” in accordance with Table 1 of Standard No. 101.
(4) If a separate indicator is provided for application of the parking brake as specified for S5.5.1(c), the single word “Park” or the words “Parking Brake” may be used.
(5) If a separate indicator is provided to indicate brake lining wear-out as specified in S5.5.1(d), the words “Brake Wear” shall be used.
(6) If a separate indicator is provided for the condition specified in S5.5.1(g), the letters and background shall be of contrasting colors, one of which is yellow. The indicator shall be labeled with the symbol “RBS.” RBS failure in a system that is part of the service brake system may also be indicated by a yellow lamp that also indicates “ABS” failure and displays the symbol “ABS/RBS.”
(7) If a separate indicator is provided for any other function, the display shall include the word “Brake” and the appropriate additional labeling.
S5.6. Brake system integrity. Each vehicle shall meet the complete performance requirements of this standard without:
(a) Detachment or fracture of any component of the braking system, such as brake springs and brake shoes or disc pad facings other than minor cracks that do not impair attachment of the friction facings. All mechanical components of the braking system shall be intact and functional. Friction facing tearout (complete detachment of lining) shall not exceed 10 percent of the lining on any single frictional element.
(b) Any visible brake fluid or lubricant on the friction surface of the brake, or leakage at the master cylinder or brake power unit reservoir cover, seal, and filler openings.
S6. General test conditions. Each vehicle must meet the performance requirements specified in S7 under the following test conditions and in accordance with the test procedures and test sequence specified. Where a range of conditions is specified, the vehicle must meet the requirements at all points within the range.
S6.1. Ambient conditions.
S6.1.1. Ambient temperature. The ambient temperature is any temperature between 0 °C (32 °F) and 40 °C (104 °F).
S6.1.2. Wind speed. The wind speed is not greater than 5 m/s (11.2 mph).
S6.2. Road test surface.
S6.2.1. Pavement friction. Unless otherwise specified, the road test surface produces a peak friction coefficient (PFC) of 1.02 when measured using an ASTM F2493 standard reference test tire, in accordance with ASTM E1337-19 (incorporated by reference, see § 571.5), at a speed of 64.4 km/h (40 mph), without water delivery.
S6.2.2. Gradient. Except for the parking brake gradient holding test, the test surface has no more than a 1% gradient in the direction of testing and no more than a 2% gradient perpendicular to the direction of testing.
S6.2.3. Lane width. Road tests are conducted on a test lane 3.5 m (11.5 ft) wide.
S6.3. Vehicle conditions.
S6.3.1. Vehicle weight.
S6.3.1.1. For the tests at GVWR, the vehicle is loaded to its GVWR such that the weight on each axle as measured at the tire-ground interface is in proportion to its GAWR, with the fuel tank filled to 100% of capacity. However, if the weight on any axle of a vehicle at LLVW exceeds the axle's proportional share of the GVWR, the load required to reach GVWR is placed so that the weight on that axle remains the same as at LLVW.
S6.3.1.2. For the test at LLVW, the vehicle is loaded to its LLVW such that the added weight is distributed in the front passenger seat area.
S6.3.2. Fuel tank loading. The fuel tank is filled to 100% of capacity at the beginning of testing and may not be less than 75% of capacity during any part of the testing.
S6.3.3. Lining preparation. At the beginning of preparation for the road tests, the brakes of the vehicle are in the same condition as when the vehicle was manufactured. No burnishing or other special preparation is allowed, unless all vehicles sold to the public are similarly prepared as a part of the manufacturing process.
S6.3.4. Adjustments and repairs. These requirements must be met without replacing any brake system parts or making any adjustments to the brake system except as specified in this standard. Where brake adjustments are specified (S7.1.3), adjust the brakes, including the parking brakes, in accordance with the manufacturer's recommendation. No brake adjustments are allowed during or between subsequent tests in the test sequence.
S6.3.5. Automatic brake adjusters. Automatic adjusters are operational throughout the entire test sequence. They may be adjusted either manually or by other means, as recommended by the manufacturer, only prior to the beginning of the road test sequence.
S6.3.6. Antilock brake system (ABS). If a car is equipped with an ABS, the ABS is fully operational for all tests, except where specified in the following sections.
S6.3.7. Variable brake proportioning valve. If a car is equipped with a variable brake proportioning system, the proportioning valve is fully operational for all tests except the test for failed variable brake proportioning system.
S6.3.8. Tire inflation pressure. Tires are inflated to the pressure recommended by the vehicle manufacturer for the GVWR of the vehicle.
S6.3.9. Engine. Engine idle speed and ignition timing are set according to the manufacturer's recommendations. If the vehicle is equipped with an adjustable engine speed governor, it is adjusted according to the manufacturer's recommendations.
S6.3.10. Vehicle openings. All vehicle openings (doors, windows, hood, trunk, convertible top, cargo doors, etc.) are closed except as required for instrumentation purposes.
S6.3.11 State of charge of batteries for EVs.
S6.3.11.1 The state of charge of the propulsion batteries is determined in accordance with SAE Recommended Practice J227a (1976) (incorporated by reference, see § 571.5). The applicable sections of J227a (1976) are 3.2.1 through 3.2.4, 3.3.1 through 3.3.2.2, 3.4.1 and 3.4.2, 4.2.1, 5.2, 5.2.1 and 5.3.
S6.3.11.2 At the beginning of the burnish procedure (S7.1 of this standard) in the test sequence, each propulsion battery is at the maximum state of charge recommended by the manufacturer, as stated in the vehicle operator's manual or on a label that is permanently attached to the vehicle, of, if the manufacturer has made no recommendation, not less than 95 percent. During the 200-stop burnish procedure, the propulsion batteries are restored to the maximum state of charge determined as above, after each increment of 40 burnish stops until the burnish procedure is complete. The batteries may be charged at a more frequent interval during a particular 40-stop increment only if the EV is incapable of achieving the initial burnish test speed during that increment. During the burnish procedure, the propulsion batteries may be charged by external means or replaced by batteries that are at a state of charge of not less than 95 percent. For an EV having a manual control for setting the level of regenerative braking, the manual control, at the beginning of the burnish procedure, is set to provide maximum regenerative braking throughout the burnish.
S6.3.11.3 At the beginning of each performance test in the test sequence (S7.2 through S7.17 of this standard), unless otherwise specified, an EV's propulsion batteries are at the state of charge recommended by the manufacturer, as stated in the vehicle operator's manual or on a label that is permanently attached to the vehicle, or, if the manufacturer has made no recommendation, at a state of charge of not less than 95 percent. No further charging of any propulsion battery occurs during any of the performance tests in the test sequence of this standard. If the propulsion batteries are depleted during a test sequence such that the vehicle reaches automatic shut-down, will not accelerate, or the low state of charge brake warning lamp is illuminated, the vehicle is to be accelerated to brake test speed by auxiliary means. If a battery is replaced rather than recharged, the replacement battery shall be charged and measured for state of charge in accordance with these procedures.
S6.3.12 State of charge of batteries for electrically-actuated service brakes. A vehicle equipped with electrically-actuated service brakes also performs the following test series. Conduct 10 stopping tests from a speed of 100 kph or the maximum vehicle speed, whichever is less. At least two of the 10 stopping distances must be less than or equal to 70 meters. The vehicle is loaded to GVWR and the transmission is in the neutral position when the service brake control is actuated and throughout the remainder of the test. Each battery providing power to the electrically-actuated service brakes, shall be in a depleted state of charge for conditions (a), (b), or (c) of this paragraph as appropriate. An auxiliary means may be used to accelerate an EV to test speed.
(a) For an EV equipped with electrically-actuated service brakes deriving power from the propulsion batteries and with automatic shut-down capability of the propulsion motor(s), the propulsion batteries are at not more than five percent above the EV actual automatic shut-down critical value. The critical value is determined by measuring the state-of-charge of each propulsion battery at the instant that automatic shut-down occurs.
(b) For an EV equipped with electrically-actuated service brakes deriving power from the propulsion batteries and with no automatic shut-down capability of the propulsion motor(s), the propulsion batteries are at an average of not more than five percent above the actual state of charge at which the brake failure warning signal, required by S5.5.1(e) of this standard, is illuminated.
(c) For a vehicle which has one or more auxiliary batteries that provides electrical energy to operate the electrically-actuated service brakes, each auxiliary battery is at not more than five percent above the actual state of charge at which the brake failure warning signal, required by S5.5.1(e) of this standard, is illuminated.
S6.3.13 Electric vehicles.
S6.3.13.1 (a) For an EV equipped with an RBS that is part of the service brake system, the RBS is operational during the burnish and all tests, except for the test of a failed RBS.
(b) For an EV equipped with an RBS that is not part of the service brake system, the RBS is operational and set to produce the maximum regenerative braking effect during the burnish, and is disabled during the test procedures. If the vehicle is equipped with a neutral gear that automatically disables the RBS, the test procedures which are designated to be conducted in gear may be conducted in neutral.
S6.3.13.2 For tests conducted “in neutral”, the operator of an EV with no “neutral” position (or other means such as a clutch for disconnecting the drive train from the propulsion motor(s)) does not apply any electromotive force to the propulsion motor(s). Any electromotive force that is applied to the propulsion motor(s) automatically remains in effect unless otherwise specified by the test procedure.
S6.4. Instrumentation.
S6.4.1. Brake temperature measurement. The brake temperature is measured by plug-type thermocouples installed in the approximate center of the facing length and width of the most heavily loaded shoe or disc pad, one per brake, as shown in Figure 1. A second thermocouple may be installed at the beginning of the test sequence if the lining wear is expected to reach a point causing the first thermocouple to contact the metal rubbing surface of a drum or rotor. For center-grooved shoes or pads, thermocouples are installed within 3 mm (.12 in) to 6 mm (.24 in) of the groove and as close to the center as possible.
S6.4.2. Brake line pressure measurement for the torque wheel test. The vehicle shall be fitted with pressure transducers in each hydraulic circuit. On hydraulically proportioned circuits, the pressure transducer shall be downstream of the operative proportioning valve.
S6.4.3. Brake torque measurement for the torque wheel test. The vehicle shall be fitted with torque wheels at each wheel position, including slip ring assemblies and wheel speed indicators to permit wheel lock to be detected.
S6.5. Procedural conditions.
S6.5.1. Brake control. All service brake system performance requirements, including the partial system requirements of S7.7, S7.10 and S7.11, must be met solely by use of the service brake control.
S6.5.2. Test speeds. If a vehicle is incapable of attaining the specified normal test speed, it is tested at a speed that is a multiple of 5 km/h (3.1 mph) that is 4 to 8 km/h (2.5 to 5.0 mph) less than its maximum speed and its performance must be within a stopping distance given by the formula provided for the specific requirement.
S6.5.3. Stopping distance.
S6.5.3.1. The braking performance of a vehicle is determined by measuring the stopping distance from a given initial speed.
S6.5.3.2. Unless otherwise specified, the vehicle is stopped in the shortest distance achievable (best effort) on all stops. Where more than one stop is required for a given set of test conditions, a vehicle is deemed to comply with the corresponding stopping distance requirements if at least one of the stops is made within the prescribed distance.
S6.5.3.3. In the stopping distance formulas given for each applicable test (such as S≤0.10V + 0.0060V 2 ), S is the maximum stopping distance in meters, and V is the test speed in km/h.
S6.5.4. Vehicle position and attitude.
S6.5.4.1. The vehicle is aligned in the center of the lane at the start of each brake application. Steering corrections are permitted during each stop.
S6.5.4.2. Stops are made without any part of the vehicle leaving the lane and without rotation of the vehicle about its vertical axis of more than ±15° from the center line of the test lane at any time during any stop.
S6.5.5. Transmission selector control.
S6.5.5.1. For tests in neutral, a stop or snub is made in accordance with the following procedures:
(a) Exceed the test speed by 6 to 12 km/h (3.7 to 7.5 mph);
(b) Close the throttle and coast in gear to approximately 3 km/h (1.9 mph) above the test speed;
(c) Shift to neutral; and
(d) When the test speed is reached, apply the brakes.
S6.5.5.2. For tests in gear, a stop or snub is made in accordance with the following procedures:
(a) With the transmission selector in the control position recommended by the manufacturer for driving on a level surface at the applicable test speed, exceed the test speed by 6 to 12 km/h (3.7 to 7.5 mph);
(b) Close the throttle and coast in gear; and
(c) When the test speed is reached apply the brakes.
(d) To avoid engine stall, a manual transmission may be shifted to neutral (or the clutch disengaged) when the vehicle speed is below 30 km/h (18.6 mph).
S6.5.6. Initial brake temperature (IBT). If the lower limit of the specified IBT for the first stop in a test sequence (other than a parking brake grade holding test) has not been reached, the brakes are heated to the IBT by making one or more brake applications from a speed of 50 km/h (31.1 mph), at a deceleration rate not greater than 3 m/s 2 (9.8 fps 2 ).
S7. Road test procedures and performance requirements. Each vehicle shall meet all the applicable requirements of this section, when tested according to the conditions and procedures set forth below and in S6, in the sequence specified in Table 1:
Table 1—Road Test Sequence
S7.1. Burnish.
S7.1.1. General information. Any pretest instrumentation checks are conducted as part of the burnish procedure, including any necessary rechecks after instrumentation repair, replacement or adjustment. Instrumentation check test conditions must be in accordance with the burnish test procedure specified in S7.1.2 and S7.1.3.
S7.1.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.1.3. Test conditions and procedures. The road test surface conditions specified in S6.2 do not apply to the burnish procedure.
(a) IBT: ≤100 °C (212 °F).
(b) Test speed: 80 km/h (49.7 mph).
(c) Pedal force: Adjust as necessary to maintain specified constant deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0 m/s 2 (9.8 fps 2 ).
(e) Wheel lockup: No lockup of any wheel allowed for longer than 0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(f) Number of runs: 200 stops.
(g) Interval between runs: The interval from the start of one service brake application to the start of the next is either the time necessary to reduce the IBT to 100 °C (212 °F) or less, or the distance of 2 km (1.24 miles), whichever occurs first.
(h) Accelerate to 80 km/h (49.7 mph) after each stop and maintain that speed until making the next stop.
(i) After burnishing, adjust the brakes as specified in S6.3.4.
S7.2 Wheel lockup sequence.
S7.2.1 General information. (a) The purpose of this test is to ensure that lockup of both front wheels occurs either simultaneously with, or at a lower deceleration rate than, the lockup of both rear wheels, when tested on road surfaces affording adhesion such that wheel lockup of the first axle occurs at a braking ratio of between 0.15 and 0.80, inclusive.
(b) This test is for vehicles without antilock brake systems.
(c) This wheel lock sequence test is to be used as a screening test to evaluate a vehicle's axle lockup sequence and to determine whether the torque wheel test in S7.4 must be conducted.
(d) For this test, a simultaneous lockup of the front and rear wheels refers to the conditions when the time interval between the first occurrence of lockup of the last (second) wheel on the rear axle and the first occurrence of lockup of the last (second) wheel on the front axle is ≤0.1 second for vehicle speeds >15 km/h (9.3 mph).
(e) A front or rear axle lockup is defined as the point in time when the last (second) wheel on an axle locks up.
(f) Vehicles that lock their front axle simultaneously or at lower deceleration rates than their rear axle need not be tested to the torque wheel procedure.
(g) Vehicles which lock their rear axle at deceleration rates lower than the front axle shall also be tested in accordance with the torque wheel procedure in S7.4.
(h) Any determination of noncompliance for failing adhesion utilization requirements shall be based on torque wheel test results.
S7.2.2 Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
S7.2.3. Test Conditions and Procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 65 km/h (40.4 mph) for a braking ratio ≤0.50; 100 km/h (62.1 mph) for a braking ratio >0.50.
(c) Pedal force:
(1) Pedal force is applied and controlled by the vehicle driver or by a mechanical brake pedal actuator.
(2) Pedal force is increased at a linear rate such that the first axle lockup occurs no less than one-half (0.5) second and no more than one and one-half (1.5) seconds after the initial application of the pedal.
(3) The pedal is released when the second axle locks, or when the pedal force reaches 1kN (225 lbs), or 0.1 seconds after first axle lockup, whichever occurs first.
(d) Wheel lockup: Only wheel lockups above a vehicle speed of 15 km/h (9.3 mph) are considered in determining the results of this test.
(e) Test surfaces: This test is conducted, for each loading condition, on two different test surfaces that will result in a braking ratio of between 0.15 and 0.80, inclusive. NHTSA reserves the right to choose the test surfaces to be used based on adhesion utilization curves or any other method of determining “worst case” conditions.
(f) The data recording equipment shall have a minimum sampling rate of 40 Hz.
(g) Data to be recorded. The following information must be automatically recorded in phase continuously throughout each test run such that values of the variables can be cross referenced in real time.
(1) Vehicle speed.
(2) Brake pedal force.
(3) Angular velocity at each wheel.
(4) Actual instantaneous vehicle deceleration or the deceleration calculated by differentiation of the vehicle speed.
(h) Speed channel filtration. For analog instrumentation, the speed channel shall be filtered by using a low-pass filter having a cut-off frequency of less than one fourth the sampling rate.
(i) Test procedure. For each test surface, three runs meeting the pedal force application and time for wheel lockup requirements shall be made. Up to a total of six runs will be allowed to obtain three valid runs. Only the first three valid runs obtained shall be used for data analysis purposes.
S7.2.4. Performance requirements. (a) In order to pass this test a vehicle shall be capable of meeting the test requirements on all test surfaces that will result in a braking ratio of between 0.15 and 0.80, inclusive.
(b) If all three valid runs on each surface result in the front axle locking before or simultaneously with the rear axle, or the front axle locks up with only one or no wheels locking on the rear axle, the torque wheel procedure need not be run, and the vehicle is considered to meet the adhesion utilization requirements of this Standard. This performance requirement shall be met for all vehicle braking ratios between 0.15 and 0.80.
(c) If any one of the three valid runs on any surface results in the rear axle locking before the front axle or the rear axle locks up with only one or no wheels locking on the front axle the torque wheel procedure shall be performed. This performance requirement shall be met for all vehicle braking ratios between 0.15 and 0.80.
(d) If any one of the three valid runs on any surface results in neither axle locking (i.e., only one or no wheels locked on each axle) before a pedal force of 1kN (225 lbs) is reached, the vehicle shall be tested to the torque wheel procedure.
(e) If the conditions listed in paragraph (c) or (d) of this section occur, vehicle compliance shall be determined from the results of a torquesults of a torque wheel test performed in accordance with S7.4.
(f) An EV with RBS that is part of the service brake system shall meet the performance requirements over the entire normal operating range of the RBS.
S7.3. ABS performance. [Reserved]
S7.4. Adhesion utilization (Torque Wheel Method).
S7.4.1. General information. This test is for vehicles without any ABS. The purpose of the test is to determine the adhesion utilization of a vehicle.
S7.4.2. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
(c) Tires: For this test, a separate set of tires, identical to those used for all other tests under Section 7.0, may be used.
S7.4.3. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speeds: 100 km/h (62.1 mph), and 50 km/h (31.1 mph).
(c) Pedal force: Pedal force is increased at a linear rate between 100 and 150 N/sec (22.5 and 33.7 lbs/sec) for the 100 km/h test speed, or between 100 and 200 N/sec (22.5 and 45.0 lbs/sec) for the 50 km/h test speed, until the first axle locks or until a pedal force of 1 kN (225 lbs) is reached, whichever occurs first.
(d) Cooling: Between brake applications, the vehicle is driven at speeds up to 100 km/h (62.1 mph) until the IBT specified in S7.4.3(a) is reached.
(e) Number of runs: With the vehicle at LLVW, run five stops from a speed of 100 km/h (62.1 mph) and five stops from a speed of 50 km/h (31.1 mph), while alternating between the two test speeds after each stop. With the vehicle at GVWR, repeat the five stops at each test speed while alternating between the two test speeds.
(f) Test surface: PFC of at least 1.02.
(g) Data to be recorded. The following information must be automatically recorded in phase continuously throughout each test run such that values of the variables can be cross referenced in real time:
(1) Vehicle speed.
(2) Brake pedal force.
(3) Angular velocity at each wheel.
(4) Brake torque at each wheel.
(5) Hydraulic brake line pressure in each brake circuit. Hydraulically proportioned circuits shall be fitted with transducers on at least one front wheel and one rear wheel downstream of the operative proportioning or pressure limiting valve(s).
(6) Vehicle deceleration.
(h) Sample rate: All data acquisition and recording equipment shall support a minimum sample rate of 40 Hz on all channels.
(i) Determination of front versus rear brake pressure. Determine the front versus rear brake pressure relationship over the entire range of line pressures. Unless the vehicle has a variable brake proportioning system, this determination is made by static test. If the vehicle has a variable brake proportioning system, dynamic tests are run with the vehicle both empty and loaded. 15 snubs from 50 km/h (31.1 mph) are made for each of the two load conditions, using the same initial conditions specified in this section.
S7.4.4. Data reduction. (a) The data from each brake application under S7.4.3 is filtered using a five-point, on-center moving average for each data channel.
(b) For each brake application under S7.4.3 determine the slope (brake factor) and pressure axis intercept (brake hold-off pressure) of the linear least squares equation best describing the measured torque output at each braked wheel as a function of measured line pressure applied at the same wheel. Only torque output values obtained from data collected when the vehicle deceleration is within the range of 0.15g to 0.80g are used in the regression analysis.
(c) Average the results of paragraph (b) of this section to calculate the average brake factor and brake hold-off pressure for all brake applications for the front axle.
(d) Average the results of paragraph (b) of this section to calculate the average brake factor and brake hold-off pressure for all brake applications for the rear axle.
(e) Using the relationship between front and rear brake line pressure determined in S7.4.3(i) and the tire rolling radius, calculate the braking force at each axle as a function of front brake line pressure.
(f) Calculate the braking ratio of the vehicle as a function of the front brake line pressure using the following equation:
(g) Calculate the adhesion utilized at each axle as a function of braking ratio using the following equations:
(h) Plot f 1 and f 2 obtained in (g) as a function of z, for both GVWR and LLVW load conditions. These are the adhesion utilization curves for the vehicle, which are compared to the performance requirements in S7.4.5. shown graphically in Figure 2:
S7.4.5. Performance requirements. For all braking ratios between 0.15 and 0.80, each adhesion utilization curve for a rear axle shall be situated below a line defined by z = 0.9k where z is the braking ratio and k is the PFC.
S7.4.5.1 An EV with RBS that is part of the service brake system shall meet the performance requirement over the entire normal operating range of the RBS.
S7.5. Cold effectiveness.
S7.5.1. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
S7.5.2. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65N (14.6 lbs), ≤500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) For each stop, bring the vehicle to test speed and then stop the vehicle in the shortest possible distance under the specified conditions.
S7.5.3. Performance requirements. (a) Stopping distance for 100 km/h test speed: ≤70m (230 ft).
(b) Stopping distance for reduced test speed: S≤0.10V + 0.0060V 2 .
S7.6. High speed effectiveness. This test is not run if vehicle maximum speed is less than or equal to 125 km/h (77.7 mph).
S7.6.1. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In gear.
S7.6.2. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 80% of vehicle maximum speed if 125 km/h (77.7 mph) <vehicle maximum speed <200 km/h (124.3 mph), or 160 km/h (99.4 mph) if vehicle maximum speed ≤200 km/h (124.3 mph).
(c) Pedal force: ≤65N (14.6 lbs), ≤500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
S7.6.3. Performance requirements.
Stopping distance: S≤0.10V + 0.0067V 2 .
S7.7. Stops with Engine Off.
S7.7.1. General information. This test is for vehicles equipped with one or more brake power units or brake power assist units. This test is also for EVs.
S7.7.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Vehicle engine: Off (not running).
(d) Ignition key position: May be returned to “on” position after turning engine off, or a device may be used to “kill” the engine while leaving the ignition key in the “on” position.
S7.7.3. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65N (14.6 lbs), ≤500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel allowed for longer than 0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) All system reservoirs (brake power and/or assist units) are fully charged and the vehicle's engine is off (not running) at the beginning of each stop.
(h) For an EV, this test is conducted with no electrical power supplied to the vehicle's propulsion motor(s), but with the RBS and brake power or power assist still operating, unless cutting off the supply of electrical power to the propulsion motor(s) also disables those systems.
S7.7.4. Performance requirements. (a) Stopping distance for 100 km/h test speed: ≤70m (230 ft.)
(b) Stopping distance for reduced test speed: S ≤0.10V + 0.0060V 2 .
S7.8. Antilock functional failure.
S7.8.1. Vehicle conditions. (a) Vehicle loading: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.8.2. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65 N (14.6 lbs), ≤500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for more than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Functional failure simulation:
(1) Disconnect the functional power source, or any other electrical connector that creates a functional failure.
(2) Determine whether the brake system indicator is activated when any electrical functional failure of the antilock system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one antilock brake subsystem is provided, repeat test for each subsystem.
S7.8.3. Performance requirements. For service brakes on a vehicle equipped with one or more antilock systems, in the event of any single functional failure in any such system, the service brake system shall continue to operate and shall stop the vehicle as specified in S7.8.3(a) or S7.8.3(b).
(a) Stopping distance for 100 km/h test speed: ≤85 m (279 ft).
(b) Stopping distance for reduced test speed: S ≤0.10V + 0.0075V 2 .
S7.9. Variable brake proportioning system functional failure.
S7.9.1. Vehicle conditions. (a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.9.2. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65 N (14.6 lbs), ≤500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Functional failure simulation:
(1) Disconnect the functional power source or mechanical linkage to render the variable brake proportioning system inoperative.
(2) If the system utilizes electrical components, determine whether the brake system indicator is activated when any electrical functional failure of the variable proportioning system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one variable brake proportioning subsystem is provided, repeat the test for each subsystem.
S7.9.3. Performance requirements. The service brakes on a vehicle equipped with one or more variable brake proportioning systems, in the event of any single functional failure in any such system, shall continue to operate and shall stop the vehicle as specified in S7.9.3(a) or S7.9.3(b).
(a) Stopping distance for 100 km/h test speed: ≤110 m (361 ft).
(b) Stopping distance for reduced test speed: S ≤0.10V + 0.0100V 2 .
S7.10. Hydraulic circuit failure.
S7.10.1. General information. This test is for vehicles manufactured with or without a split service brake system.
S7.10.2. Vehicle conditions. (a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.10.3. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65N (14.6 lbs), ≤500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Test surface: PFC of 1.02.
(f) Alter the service brake system to produce any single failure. For a hydraulic circuit, this may be any single rupture or leakage type failure, other than a structural failure of a housing that is common to two or more subsystems. For a vehicle in which the brake signal is transmitted electrically between the brake pedal and some or all of the foundation brakes, regardless of the means of actuation of the foundation brakes, this may be any single failure in any circuit that electrically transmits the brake signal. For an EV with RBS that is part of the service brake system, this may be any single failure in the RBS.
(g) Determine the control force pressure level or fluid level (as appropriate for the indicator being tested) necessary to activate the brake warning indicator.
(h) Number of runs: After the brake warning indicator has been activated, make the following stops depending on the type of brake system:
(1) 4 stops for a split service brake system.
(2) 10 consecutive stops for a non-split service brake system.
(i) Each stop is made by a continuous application of the service brake control.
(j) Restore the service brake system to normal at the completion of this test.
(k) Repeat the entire sequence for each of the other subsystems.
S7.10.4 Performance requirements. For vehicles manufactured with a split service brake system, in the event of any failure in a single subsystem, as specified in S7.10.3(f) of this standard, and after activation of the brake system indicator as specified in S5.5.1, the remaining portions of the service brake system shall continue to operate and shall stop the vehicle as specified in S7.10.4(a) or S7.10.4(b). For vehicles not manufactured with a split service brake system, in the event of any failure in any component of the service brake system, as specified in S7.10.3(f), and after activation of the brake system indicator as specified in S5.5.1 of this standard, the vehicle shall, by operation of the service brake control, stop 10 times consecutively as specified in S7.10.4(a) or S7.10.4(b).
(a) Stopping distance from 100 km/h test speed: ≤168 m (551 ft).
(b) Stopping distance for reduced test speed: S ≤0.10V + 0.0158V 2 .
S7.11. Brake power unit or brake power assist unit inoperative (System depleted).
S7.11.1. General information. This test is for vehicles equipped with one or more brake power units or brake power assist units.
S7.11.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.11.3. Test conditions and procedures. (a) IBT: ≤65 °C (149 °F), ≤100 °C (212 °F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: ≤65 N (14.6 lbs), ≤500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Disconnect the primary source of power for one brake power assist unit or brake power unit, or one of the brake power unit or brake power assist unit subsystems if two or more subsystems are provided.
(h) If the brake power unit or power assist unit operates in conjunction with a backup system and the backup system is automatically activated in the event of a primary power service failure, the backup system is operative during this test.
(i) Exhaust any residual brake power reserve capability of the disconnected system.
(j) Make each of the 6 stops by a continuous application of the service brake control.
(k) Restore the system to normal at completion of this test.
(l) For vehicles equipped with more than one brake power unit or brake power assist unit, conduct tests for each in turn.
(m) For vehicles with electrically-actuated service brakes (brake power unit), this test is conducted with any single electrical failure in the electrically-actuated service brakes instead of a failure of any other brake power or brake power assist unit, and all other systems intact.
S7.11.4. Performance requirements. The service brakes on a vehicle equipped with one or more brake power assist units or brake power units, with one such unit inoperative and depleted of all reserve capability, shall stop the vehicle as specified in S7.11.4(a) or S7.11.4(b).
(a) Stopping distance from 100 km/h test speed: ≤168 m (551 ft).
(b) Stopping distance for reduced test speed: S ≤0.10V + 0.0158V 2 .
S7.12. Parking brake.
S7.12.1. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Parking brake burnish:
(1) For vehicles with parking brake systems not utilizing the service friction elements, the friction elements of such a system are burnished prior to the parking brake test according to the published recommendations furnished to the purchaser by the manufacturer.
(2) If no recommendations are furnished, the vehicle's parking brake system is tested in an unburnished condition.
(d) Parking brake applications: 1 application and up to 2 reapplications, if necessary.
S7.12.2. Test conditions and procedures.
(a) IBT:
(1) Parking brake systems utilizing service brake friction materials shall be tested with the IBT ≤100 °C (212 °F) and shall have no additional burnishing or artificial heating prior to the start of the parking brake test.
(2) Parking brake systems utilizing non-service brake friction materials shall be tested with the friction materials at ambient temperature at the start of the test. The friction materials shall have no additional burnishing or artificial heating prior to or during the parking brake test.
(b) Parking brake control force: Hand control ≤400 N (89.9 lbs); foot control ≤500 N (112.4 lbs).
(c) Hand force measurement locations: The force required for actuation of a hand-operated brake system is measured at the center of the hand grip area or at a distance of 40 mm (1.57 in) from the end of the actuation lever as illustrated in Figure 3.
(d) Parking brake applications: 1 application and up to 2 reapplications, if necessary.
(e) Test surface gradient: 20% grade.
(f) Drive the vehicle onto the grade with the longitudinal axis of the vehicle in the direction of the slope of the grade.
(g) Stop the vehicle and hold it stationary by applying the service brake control and place the transmission in neutral.
(h) With the service brake applied sufficiently to just keep the vehicle from rolling, apply the parking brake as specified in S7.12.2(i) or S7.12.2(j).
(i) For a vehicle equipped with mechanically-applied parking brakes, make a single application of the parking brake control with a force not exceeding the limits specified in S7.12.2(b). For a vehicle using an electrically-activated parking brake, apply the parking brake by activating the parking brake control.
(j) In the case of a parking brake system that does not allow application of the specified force in a single application, a series of applications may be made to achieve the specified force.
(k) Following the application of the parking brakes, release all force on the service brake control and, if the vehicle remains stationary, start the measurement of time.
(l) If the vehicle does not remain stationary, reapplication of a force to the parking brake control at the level specified in S7.12.2(b) as appropriate for the vehicle being tested (without release of the ratcheting or other holding mechanism of the parking brake) is used up to two times to attain a stationary position.
(m) Verify the operation of the parking brake application indicator.
(n) Following observation of the vehicle in a stationary condition for the specified time in one direction, repeat the same test procedure with the vehicle orientation in the opposite direction on the same grade.
S7.12.3. Performance requirement. The parking brake system shall hold the vehicle stationary for 5 minutes in both a forward and reverse direction on the grade.
S7.13. Heating Snubs.
S7.13.1. General information. The purpose of the snubs is to heat up the brakes in preparation for the hot performance test which follows immediately.
S7.13.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.13.3. Test conditions and procedures. (a) IBT:
(1) Establish an IBT before the first brake application (snub) of ≤55 °C (131 °F), ≤65 °C (149 °F).
(2) IBT before subsequent snubs are those occurring at the distance intervals.
(b) Number of snubs: 15.
(c) Test speeds: The initial speed for each snub is 120 km/h (74.6 mph) or 80% of Vmax, whichever is slower. Each snub is terminated at one-half the initial speed.
(d) Deceleration rate:
(1) Maintain a constant deceleration rate of 3.0 m/s 2 (9.8 fps 2 ).
(2) Attain the specified deceleration within one second and maintain it for the remainder of the snub.
(e) Pedal force: Adjust as necessary to maintain the specified constant deceleration rate.
(f) Time interval: Maintain an interval of 45 seconds between the start of brake applications (snubs).
(g) Accelerate as rapidly as possible to the initial test speed immediately after each snub.
(h) Immediately after the 15th snub, accelerate to 100 km/h (62.1 mph) and commence the hot performance test.
S7.14. Hot performance.
S7.14.1. General information. The hot performance test is conducted immediately after completion of the 15th heating snub.
S7.14.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.14.3. Test conditions and procedures. (a) IBT: Temperature achieved at completion of heating snubs.
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force:
(1) The first stop is done with an average pedal force not greater than the average pedal force recorded during the shortest GVWR cold effectiveness stop.
(2) The second stop is done with a pedal force not greater than 500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the 15th heating snub, accelerate to 100 km/h (62.1 mph) and commence the first stop of the hot performance test.
(g) If the vehicle is incapable of attaining 100 km/h, it is tested at the same speed used for the GVWR cold effectiveness test.
(h) Immediately after completion of the first hot performance stop, accelerate as rapidly as possible to the specified test speed and conduct the second hot performance stop.
(i) Immediately after completion of the second hot performance stop, drive 1.5 km (0.93 mi) at 50 km/h (31.1 mph) before the first cooling stop.
S7.14.4. Performance requirements. (a) For the first hot stop, the stopping distance must be less than or equal to a calculated distance which is based on 60 percent of the deceleration actually achieved on the shortest GVWR cold effectiveness stop. The following equations shall be used in calculating the performance requirement:
(b) In addition to the requirement in S7.14.4(a), the stopping distance for at least one of the two hot stops must be S ≤89 m (292 ft) from a test speed of 100 km/h (62.1 mph) or, for reduced test speed, S ≤0.10V + 0.0079V 2 . The results of the second stop may not be used to meet the requirements of S7.14.4(a).
S7.15. Brake cooling stops.
S7.15.1. General information. The cooling stops are conducted immediately after completion of the hot performance test.
S7.15.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.15.3. Test conditions and procedures. (a) IBT: Temperature achieved at completion of hot performance.
(b) Test speed: 50 km/h (31.1 mph).
(c) Pedal force: Adjust as necessary to maintain specified constant deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0 m/s 2 (9.8 fps 2 ).
(e) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15
(f) Number of runs: 4 stops.
(g) Immediately after the hot performance stops drive 1.5 km (0.93 mi) at 50 km/h (31.1 mph) before the first cooling stop.
(h) For the first through the third cooling stops:
(1) After each stop, immediately accelerate at the maximum rate to 50 km/h (31.1 mph).
(2) Maintain that speed until beginning the next stop at a distance of 1.5 km (0.93 mi) from the beginning of the previous stop.
(i) For the fourth cooling stop:
(1) Immediately after the fourth stop, accelerate at the maximum rate to 100 km/h (62.1 mph).
(2) Maintain that speed until beginning the recovery performance stops at a distance of 1.5 km (0.93 mi) after the beginning of the fourth cooling stop.
S7.16. Recovery performance.
S7.16.1. General information. The recovery performance test is conducted immediately after completion of the brake cooling stops.
S7.16.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.16.3. Test conditions and procedures. (a) IBT: Temperature achieved at completion of cooling stops.
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: The average pedal force shall not be greater than the average pedal force recorded during the shortest GVWR cold effectiveness stop.
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the fourth cooling stop, accelerate at the maximum rate to 100 km/h (62.1 mph).
(g) Maintain that speed until beginning the first recovery performance stop at a distance of 1.5 km (0.93 mi) after the beginning of the fourth cooling stop.
(h) If the vehicle is incapable of attaining 100 km/h, it is tested at the same speed used for the GVWR cold effectiveness test.
(i) Immediately after completion of the first recovery performance stop accelerate as rapidly as possible to the specified test speed and conduct the second recovery performance stop.
S7.16.4. Performance requirements.
The stopping distance, S, for at least one of the two stops must be within the following limits:
S7.17. Final Inspection. Inspect:
(a) The service brake system for detachment or fracture of any components, such as brake springs and brake shoes or disc pad facings.
(b) The friction surface of the brake, the master cylinder or brake power unit reservoir cover, and seal and filler openings, for leakage of brake fluid or lubricant.
(c) The master cylinder or brake power unit reservoir for compliance with the volume and labeling requirements of S5.4.2 and S5.4.3. In determining the fully applied worn condition, assume that the lining is worn to (1) rivet or bolt heads on riveted or bolted linings or (2) within 0.8 mm (1/32 inch) of shoe or pad mounting surface on bonded linings or (3) the limit recommended by the manufacturer, whichever is larger relative to the total possible shoe or pad movement. Drums or rotors are assumed to be at nominal design drum diameter or rotor thickness. Linings are assumed adjusted for normal operating clearance in the released position.
(d) The brake system indicators, for compliance with operation in various key positions, lens color, labeling, and location, in accordance with S5.5.
§ 571.136   Standard No. 136; Electronic stability control systems for heavy vehicles.
S1 Scope. This standard establishes performance and equipment requirements for electronic stability control (ESC) systems on heavy vehicles.
S2 Purpose. The purpose of this standard is to reduce crashes caused by rollover or by directional loss-of-control.
S3 Application. This standard applies to the following vehicles:
S3.1 Truck tractors with a gross vehicle weight rating of greater than 11,793 kilograms (26,000 pounds). However, it does not apply to:
(a) Any truck tractor equipped with an axle that has a gross axle weight rating of 13,154 kilograms (29,000 pounds) or more;
(b) Any truck tractor that has a speed attainable in 3.2 km (2 miles) of not more than 53 km/h (33 mph); and
(c) Any truck tractor that has a speed attainable in 3.2 km (2 miles) of not more than 72 km/h (45 mph), an unloaded vehicle weight that is not less than 95 percent of its gross vehicle weight rating, and no capacity to carry occupants other than the driver and operating crew.
S3.2 Buses with a gross vehicle weight rating of greater than 11,793 kilograms (26,000 pounds). However, it does not apply to
(a) School buses;
(b) Perimeter-seating buses;
(c) Transit buses;
(d) Any bus equipped with an axle that has a gross axle weight rating of 13,154 kilograms (29,000 pounds) or more; and
(e) Any bus that has a speed attainable in 3.2 km (2 miles) of not more than 53 km/h (33 mph.)
S4 Definitions.
Ackerman Steer Angle means the angle whose tangent is the wheelbase divided by the radius of the turn at a very low speed.
Electronic stability control system or ESC system means a system that has all of the following attributes:
(1) It augments vehicle directional stability by having the means to apply and adjust the vehicle brake torques individually at each wheel position on at least one front and at least one rear axle of the truck tractor or bus to induce correcting yaw moment to limit vehicle oversteer and to limit vehicle understeer;
(2) It enhances rollover stability by having the means to apply and adjust the vehicle brake torques individually at each wheel position on at least one front and at least one rear axle of the truck tractor or bus to reduce lateral acceleration of a vehicle;
(3) It is computer-controlled with the computer using a closed-loop algorithm to induce correcting yaw moment and enhance rollover stability;
(4) It has a means to determine the vehicle's lateral acceleration;
(5) It has a means to determine the vehicle's yaw rate and to estimate its side slip or side slip derivative with respect to time;
(6) It has a means to estimate vehicle mass or, if applicable, combination vehicle mass;
(7) It has a means to monitor driver steering inputs;
(8) It has a means to modify engine torque, as necessary, to assist the driver in maintaining control of the vehicle and/or combination vehicle; and
(9) When installed on a truck tractor, it has the means to provide brake pressure to automatically apply and modulate the brake torques of a towed trailer.
ESC service brake application means the time when the ESC system applies a service brake pressure at any wheel for a continuous duration of at least 0.5 second of at least 34 kPa (5 psi) for air-braked systems and at least 172 kPa (25 psi) for hydraulic-braked systems.
Initial brake temperature means the average temperature of the service brakes on the hottest axle of the vehicle immediately before any stability control system test maneuver is executed.
Lateral acceleration means the component of the vector acceleration of a point in the vehicle perpendicular to the vehicle x-axis (longitudinal) and parallel to the road plane.
Oversteer means a condition in which the vehicle's yaw rate is greater than the yaw rate that would occur at the vehicle's speed as result of the Ackerman Steer Angle.
Over-the-road bus means a bus characterized by an elevated passenger deck located over a baggage compartment, except a school bus.
Peak friction coefficient or PFC means the ratio of the maximum value of braking test wheel longitudinal force to the simultaneous vertical force occurring prior to wheel lockup, as the braking torque is progressively increased.
Perimeter-seating bus means a bus with 7 or fewer designated seating positions rearward of the driver's seating position that are forward-facing or can convert to forward-facing without the use of tools and is not an over-the-road bus.
Side slip or side slip angle means the arctangent of the lateral velocity of the center of gravity of the vehicle divided by the longitudinal velocity of the center of gravity.
Snub means the braking deceleration of a vehicle from a higher speed to a lower speed that is greater than zero.
Stop-request system means a vehicle-integrated system for passenger use to signal to a vehicle operator that they are requesting a stop.
Tandem axle means a group or set of two or more axles placed in close arrangement, one behind the other, with the centerlines of adjacent axles not more than 72 inches apart.
Transit bus means a bus that is equipped with a stop-request system sold for public transportation provided by, or on behalf of, a State or local government and that is not an over-the-road bus.
Understeer means a condition in which the vehicle's yaw rate is less than the yaw rate that would occur at the vehicle's speed as result of the Ackerman Steer Angle.
Wheelbase means the longitudinal distance between the center of the front axle and the center of the rear axle. For vehicles with tandem axles, the center of the axle is the midpoint between the centers of the most forward and most rearward tandem axles, measured when all liftable axles are in the lowered position.
Yaw Rate means the rate of change of the vehicle's heading angle measure in degrees per second of rotation about a vertical axis through the vehicle's center of gravity.
S5 Requirements. Each vehicle must be equipped with an ESC system that meets the requirements specified in S5 under the test conditions specified in S6 and the test procedures specified in S7 of this standard.
S5.1 Required Equipment. Each vehicle to which this standard applies must be equipped with an electronic stability control system, as defined in S4.
S5.2 System Operational Capabilities.
S5.2.1 The ESC system must be operational over the full speed range of the vehicle except at vehicle speeds less than 20 km/h (12.4 mph), when being driven in reverse, or during system initialization.
S5.2.2 The ESC must remain capable of activation even if the antilock brake system or traction control is also activated.
S5.3 Performance Requirements.
S5.3.1 Lane Keeping During Reference Speed Determination. During each series of four consecutive test runs conducted at the same entrance speed as part of the test procedure to determine the Preliminary Reference Speed and the Reference Speed (see S7.7.1), the wheels of the truck tractor or bus must remain within the lane between the start gate (0 degrees of radius arc angle) and the end gate (120 degrees of radius arc angle) during at least two of the four test runs.
S5.3.2 Engine Torque Reduction. During each series of four consecutive test runs for the determination of engine torque reduction (see S7.7.2), the vehicle must satisfy the criteria of S5.3.2.1 and S5.3.2.2 during at least two of the four test runs.
S5.3.2.1 The ESC system must reduce the driver-requested engine torque by at least 10 percent for a minimum continuous duration of 0.5 second during the time period from 1.5 seconds after the vehicle crosses the start gate (0 degree of radius arc angle) to when it crosses the end gate (120 degrees of radius arc angle).
S5.3.2.2 The wheels of the truck tractor or bus must remain within the lane between the start gate (0 degrees of radius arc angle) and the end gate (120 degrees of radius arc angle).
S5.3.3 Roll Stability Control Test. During each series of eight consecutive test runs for the determination of roll stability control (see S7.7.3) conducted at the same entrance speed, the vehicle must satisfy the criteria of S5.3.3.1, S5.3.3.2, S5.3.3.3, and S5.3.3.4 during at least six of the eight consecutive test runs.
S5.3.3.1 The vehicle speed measured at 3.0 seconds after vehicle crosses the start gate (0 degrees of radius arc angle) must not exceed 47 km/h (29 mph).
S5.3.3.2 The vehicle speed measured at 4.0 seconds after vehicle crosses the start gate (0 degrees of radius arc angle) must not exceed 45 km/h (28 mph).
S5.3.3.3 The wheels of the truck tractor or bus must remain within the lane between the start gate (0 degrees of radius arc angle) and the end gate (120 degrees of radius arc angle).
S5.3.3.4 There must be ESC service brake activation.
S5.4 ESC Malfunction Detection. Each vehicle must be equipped with an indicator lamp, mounted in front of and in clear view of the driver, which is activated whenever there is a malfunction that affects the generation or transmission of control or response signals in the vehicle's electronic stability control system.
S5.4.1 Except as provided in S5.4.3 and S5.4.6, the ESC malfunction telltale must illuminate only when a malfunction exists and must remain continuously illuminated for as long as the malfunction exists, whenever the ignition locking system is in the “On” (“Run”) position.
S5.4.2 The ESC malfunction telltale must be identified by the symbol shown for “Electronic Stability Control System Malfunction” or the specified words or abbreviations listed in Table 1 of Standard No. 101 (§ 571.101).
S5.4.3 The ESC malfunction telltale must be activated as a check-of-lamp function either when the ignition locking system is turned to the “On” (“Run”) position when the engine is not running, or when the ignition locking system is in a position between the “On” (“Run”) and “Start” that is designated by the manufacturer as a check-light position.
S5.4.4 The ESC malfunction telltale need not be activated when a starter interlock is in operation.
S5.4.5 The ESC malfunction telltale lamp must extinguish at the next ignition cycle after the malfunction has been corrected.
S5.4.6 The manufacturer may use the ESC malfunction telltale in a flashing mode to indicate ESC operation.
S6 Test Conditions. The requirements of S5 must be met by a vehicle when it is tested according to the conditions set forth in the S6, without replacing any brake system part or making any adjustments to the ESC system except as specified. On vehicles equipped with automatic brake adjusters, the automatic brake adjusters will remain activated at all times.
S6.1 Ambient Conditions.
S6.1.1 The ambient temperature is any temperature between 2 °C (35 °F) and 40 °C (104 °F).
S6.1.2 The maximum wind speed is no greater than 5 m/s (11 mph).
S6.2 Road Test Surface.
S6.2.1 The tests are conducted on a dry, uniform, solid-paved surface. Surfaces with irregularities and undulations, such as dips and large cracks, are unsuitable.
S6.2.2 The road test surface produces a peak friction coefficient (PFC) of 1.02 when measured using an ASTM F2493 standard reference test tire, in accordance with ASTM E1337-19, at a speed of 64.4 km/h (40 mph), without water delivery (incorporated by reference, see § 571.5).
S6.2.3 The test surface has a consistent slope between 0% and 1%.
S6.2.4 J-Turn Test Maneuver Test Course. The test course for the J-Turn test maneuver is used for the Reference Speed Test in S7.7.1, the Engine Torque Reduction Test in S7.7.2, and the Roll Stability Control Test in S7.7.3.
S6.2.4.1 The test course consists of a straight entrance lane with a length of 22.9 meters (75 feet) tangentially connected to a curved lane section with a radius of 45.7 meters (150 feet) measured from the center of the lane.
S6.2.4.2 For truck tractors, the lane width of the test course is 3.7 meters (12 feet). At the manufacturer's option, for truck tractors with a wheelbase equal to or greater than 7112 mm (280 inches) the lane width of the test course is 3.7 meters (12 feet) for the straight section and is 4.3 meters (14 feet) for the curved section. For buses, the lane width of the test course is 3.7 meters (12 feet) for the straight section and is 4.3 meters (14 feet) for the curved section.
S6.2.4.3 The start gate is the tangent point on the radius (the intersection of the straight lane and the curved lane sections) and is designated as zero degrees of radius of arc angle. The end gate is the point on the radius that is 120 degrees of radius arc angle measured from the tangent point.
S6.2.4.4 Figure 1 shows the test course with the curved lane section configured in the counter-clockwise steering direction relative to the entrance lane. The course is also arranged with the curved lane section configured in the clockwise steering direction relative to the entrance lane. The cones depicted in Figure 1 defining the lane width are positioned solely for illustrative purposes.
S6.3 Vehicle Conditions.
S6.3.1 The ESC system is enabled for all testing, except for the ESC malfunction test (see S7.8).
S6.3.2 All vehicle openings (doors, windows, hood, trunk, cargo doors, etc.) are in a closed position except as required for instrumentation purposes.
S6.3.3 Test Weight.
S6.3.3.1 Truck Tractors. A truck tractor is loaded to its GVWR by coupling it to a control trailer (see S6.3.5). The tractor is loaded with the test driver, test instrumentation, and an anti-jackknife system (see S6.3.8).
S6.3.3.2 Buses. A bus is loaded with ballast (weight) to its GVWR to simulate a multi-passenger and baggage configuration. For this configuration the bus is loaded with test driver, test instrumentation, outriggers (see S6.3.6), ballast, and a simulated occupant in each of the vehicle's designated seating positions. The simulated occupant loads are attained by securing 68 kilograms (150 pounds) of ballast in each of the test vehicle's designated seating positions. If the simulated occupant loads result in the bus being loaded to less than its GVWR, additional ballast is added to the bus in the following manner until the bus is loaded to its GVWR without exceeding any axle's GAWR: First, ballast is added to the lowest baggage compartment; second, ballast is added to the floor of the passenger compartment. If the simulated occupant loads result in the GAWR of any axle being exceeded or the GVWR of the bus being exceeded, simulated occupant loads are removed until the vehicle's GVWR and all axles' GAWR are no longer exceeded.
S6.3.4 Transmission and Brake Controls. The transmission selector control is in a forward gear during all maneuvers. A vehicle equipped with an engine braking system that is engaged and disengaged by the driver is tested with the system disengaged.
S6.3.5 Control Trailer.
S6.3.5.1 The control trailer is an unbraked, flatbed semi-trailer that has a single axle with a GAWR of 8,165 kg (18,000 lb.). The control trailer has a length of at least 6,400 mm (252 inches), but no more than 7,010 mm (276 inches), when measured from the transverse centerline of the axle to the centerline of the kingpin (the point where the trailer attaches to the truck tractor). At the manufacturer's option, truck tractors with four or more axles may use a control trailer with a length of more than 7,010 mm (276 inches), but no more than 13,208 mm (520 inches) when measured from the transverse centerline of the axle to the centerline of the kingpin.
S6.3.5.2 The location of the center of gravity of the ballast on the control trailer is directly above the kingpin. The height of the center of gravity of the ballast on the control trailer is less than 610 mm (24 inches) above the top of the tractor's fifth-wheel hitch (the area where the truck tractor attaches to the trailer).
S6.3.5.3 The control trailer is equipped with outriggers (see S6.3.6).
S6.3.5.4 A truck tractor is loaded to its GVWR by placing ballast (weight) on the control trailer which loads the tractor's non-steer axles. The control trailer is loaded with ballast without exceeding the GAWR of the trailer axle. If the tractor's fifth-wheel hitch position is adjustable, the fifth-wheel hitch is adjusted to proportionally distribute the load on each of the tractor's axle(s), according to each axle's GAWR, without exceeding the GAWR of any axle(s). If the fifth-wheel hitch position cannot be adjusted to prevent the load from exceeding the GAWR of the tractor's axle(s), the ballast is reduced until the axle load is equal to or less than the GAWR of the tractor's rear axle(s), maintaining load proportioning as close as possible to specified proportioning.
S6.3.6 Outriggers. Outriggers are used for testing each vehicle. The outriggers are designed with a maximum weight of 1,134 kg (2,500 lb.), excluding mounting fixtures.
S6.3.7 Tires. The tires are inflated to the vehicle manufacturer's specified pressure for the GVWR of the vehicle.
S6.3.8 Truck Tractor Anti-Jackknife System. A truck tractor is equipped with an anti-jackknife system that allows a minimum articulation angle of 30 degrees between the tractor and the control trailer.
S6.3.9 Special Drive Conditions. A vehicle equipped with an interlocking axle system or a front wheel drive system that is engaged and disengaged by the driver is tested with the system disengaged.
S6.3.10 Liftable Axles. A vehicle with one or more liftable axles is tested with the liftable axles down.
S6.3.11 Initial Brake Temperature. The initial brake temperature of the hottest brake for any performance test is between 66 °C (150 °F) and 204 °C (400 °F).
S6.3.12 Thermocouples. The brake temperature is measured by plug-type thermocouples installed in the approximate center of the facing length and width of the most heavily loaded shoe or disc pad, one per brake. A second thermocouple may be installed at the beginning of the test sequence if the lining wear is expected to reach a point causing the first thermocouple to contact the rubbing surface of a drum or rotor. The second thermocouple is installed at a depth of 0.080 inch and located within 1.0 inch circumferentially of the thermocouple installed at 0.040 inch depth. For center-grooved shoes or pads, thermocouples are installed within 0.125 inch to 0.250 inch of the groove and as close to the center as possible.
S6.4 Selection of Compliance Options. Where manufacturer options are specified, the manufacturer must select the option by the time it certifies the vehicle and may not thereafter select a different option for the vehicle. Each manufacturer shall, upon request from the National Highway Traffic Safety Administration, provide information regarding which of the compliance options it has selected for a particular vehicle or make/model.
S7 Test Procedure. S7.1 Tire Inflation. Inflate the vehicle's tires as specified in S6.3.7.
S7.2 Telltale Lamp Check. With the vehicle stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “On” (“Run”) position or, where applicable, the appropriate position for the lamp check. The ESC system must perform a check-of-lamp function for the ESC malfunction telltale, as specified in S5.4.3.
S7.3 Tire Conditioning. Condition the tires to wear away mold sheen and achieve operating temperature immediately before beginning the J-Turn test runs. The test vehicle is driven around a circle 150 feet (46 meters) in radius at a speed that produces a lateral acceleration of approximately 0.1g for two clockwise laps followed by two counterclockwise laps.
S7.4 Brake Conditioning and Temperature. Conditioning and warm-up of the vehicle brakes are completed before and monitored during the execution of the J-Turn test maneuver.
S7.4.1 Brake Conditioning. Condition the brakes in accordance with S7.4.1.1 and S7.4.1.2.
S7.4.1.1 Prior to executing the J-Turn test maneuver, the vehicle's brakes are burnished as follows: With the transmission in the highest gear appropriate for a speed of 64 km/h (40 mph), make 500 snubs between 64 km/h (40 mph) and 32 km/h (20 mph) at a deceleration rate of 0.3g, or at the vehicle's maximum deceleration rate if less than 0.3g. After each brake application accelerate to 64 km/h (40 mph) and maintain that speed until making the next brake application at a point 1.6 km (1.0 mile) from the initial point of the previous brake application. If the vehicle cannot attain a speed of 64 km/h (40 mph) in 1.6 km (1.0 mile), continue to accelerate until the vehicle reaches 64 km/h (40 mph) or until the vehicle has traveled 2.4 km (1.5 miles) from the initial point of the previous brake application, whichever occurs first. The brakes may be adjusted up to three times during the burnish procedure, at intervals specified by the vehicle manufacturer, and may be adjusted at the conclusion of the burnishing, in accordance with the vehicle manufacturer's recommendation.
S7.4.1.2 Prior to executing the performance tests in S7.7, the brakes are conditioned using 40 brake application snubs from a speed of 64 km/h (40 mph) to a speed of 32 km/h (20 mph), with a target deceleration of approximately 0.3g. After each brake application, accelerate to 64 km/h (40 mph) and maintain that speed until making the next brake application at a point 1.6 km (1.0 mile) from the initial point of the previous brake application.
S7.4.2 Brake Temperature. Prior to testing or any time during testing, if the hottest brake temperature is above 204 °C (400 °F) a cool down period is performed until the hottest brake temperature is measured within the range of 66 °C-204 °C (150 °F-400 °F). Prior to testing or any time during testing, if the hottest brake temperature is below 66 °C (150 °F) individual brake stops are repeated to increase any one brake temperature to within the target temperature range of 66 °C-204 °C (150 °F-400 °F) before a test maneuver is performed.
S7.5 Mass Estimation Cycle. Perform the mass estimation procedure for the ESC system according to the manufacturer's instructions. This procedure will be repeated if an ignition cycle occurs or is needed at any time between the initiation and completion of S7.7.
S7.6 ESC System Malfunction Check. Check that the ESC system is enabled by ensuring that the ESC malfunction telltale is not illuminated.
S7.7 J-Turn Test Maneuver. The truck tractor or bus is subjected to multiple series of test runs using the J-Turn test maneuver. The truck tractor or bus travels through the course by driving down the entrance lane, crossing the start gate at the designated entrance speed, turning through the curved lane section, and crossing the end gate, while the driver attempts to keep all of the wheels of the truck tractor or bus within the lane.
S7.7.1 Reference Speed Test. The vehicle is subjected to J-Turn test maneuvers to determine the Reference Speed for each steering direction. The Reference Speeds are used in S7.7.2 and S7.7.3.
S7.7.1.1 Preliminary Reference Speed Determination. The vehicle is subjected to two series of test runs using the J-Turn test maneuver at increasing entrance speeds. One series uses clockwise steering, and the other series uses counterclockwise steering. The entrance speed of a test run is the 0.5 second average of the raw speed data prior to any ESC system activation of the service brakes and rounded to the nearest 1.0 mph. During each test run, the driver attempts to maintain the selected entrance speed throughout the J-Turn test maneuver. For the first test run of each series, the entrance speed is 32 km/h ±1.6 km/h (20 mph ±1.0 mph) and is incremented 1.6 km/h (1.0 mph) for each subsequent test run until ESC service brake application occurs or any of the truck tractor's or bus's wheels departs the lane. The vehicle entrance speed at which ESC service brake application occurs is the Preliminary Reference Speed. The Preliminary Reference Speed is determined for each direction: Clockwise steering and counter-clockwise steering. During any test run, if any of the wheels of the truck tractor or bus depart the lane at any point within the first 120 degrees of radius arc angle, the test run is repeated at the same entrance speed. If any of the wheels of the truck tractor or bus depart the lane again, then four consecutive test runs are repeated at the same entrance speed (±1.6 km/h (±1.0 mph)).
S7.7.1.2 Reference Speed Determination. Using the Preliminary Reference Speed determined in S7.7.1.1, perform two series of test runs using the J-Turn test maneuver to determine the Reference Speed. The first series consists of four consecutive test runs performed using counter-clockwise steering. The second series consists of four consecutive test runs performed using clockwise steering. During each test run, the driver attempts to maintain a speed equal to the Preliminary Reference Speed throughout the J-Turn test maneuver. The Reference Speed is the minimum entrance speed at which ESC service brake application occurs for at least two of four consecutive test runs of each series conducted at the same entrance speed (within ±1.6 km/h (±1.0 mph)). The Reference Speed is determined for each direction: clockwise steering and counter-clockwise steering. If ESC service brake application does not occur during at least two test runs of either series, the Preliminary Reference Speed is increased by 1.6 km/h (1.0 mph), and the procedure in this section is repeated.
S7.7.2 Engine Torque Reduction Test. The vehicle is subjected to two series of test runs using the J-Turn test maneuver at an entrance speed equal to the Reference Speed determined in S7.7.1.2. One series uses clockwise steering, and the other series uses counter-clockwise steering. Each series consists of four test runs with the vehicle at an entrance speed equal to the Reference Speed and the driver fully depressing the accelerator pedal from the time when the vehicle crosses the start gate until the vehicle reaches the end gate. ESC engine torque reduction is confirmed by comparing the engine torque output and driver requested torque data collected from the vehicle communication network or CAN bus. During the initial stages of each maneuver the two torque signals with respect to time will parallel each other. Upon ESC engine torque reduction, the two signals will diverge when the ESC system causes a commanded engine torque reduction and the driver depresses the accelerator pedal attempting to accelerate the vehicle.
S7.7.2.1 Perform two series of test runs using the J-Turn test maneuver at the Reference Speed determined in S7.7.1.2 (±1.6 km/h (±1.0 mph)). The first series consists of four consecutive test runs performed using counter-clockwise steering. The second series consists of four consecutive test runs performed using clockwise steering. During each test run, the driver fully depresses the accelerator pedal from the time when the vehicle crosses the start gate until the vehicle reaches the end gate.
S7.7.2.2 During each of the engine torque reduction test runs, verify the commanded engine torque and the driver requested torque signals diverge according to the criteria specified in S5.3.2.1.
S7.7.3 Roll Stability Control Test. The vehicle is subjected to multiple series of test runs using the J-Turn test maneuver in both the clockwise and the counter-clockwise direction.
S7.7.3.1 Before each test run, the brake temperatures are monitored and the hottest brake is confirmed to be between 66 °C (150 °F) and 204 °C (400 °F). If the hottest brake temperature is not between 66 °C (150 °F) and 204 °C (400 °F), the brake temperature is adjusted in accordance with S7.4.2.
S7.7.3.2 During each test run, the driver will release the accelerator pedal after the ESC system has slowed vehicle by more than 4.8 km/h (3.0 mph) below the entrance speed.
S7.7.3.3 The maximum test speed is the greater of 130 percent of the Reference Speed (see S7.7.1.2) or 48 km/h (30 mph). The maximum test speed is determined for each direction: clockwise steering and counter-clockwise steering.
S7.7.3.4 For each series of Roll Stability Control test runs, the vehicle will perform eight consecutive test runs at the same entrance speed, which is any speed between 48 km/h (30 mph) and the maximum test speed determined according to S7.7.3.3.
S7.7.3.5 Upon completion of testing, post processing is done as specified in S7.9.
S7.8 ESC Malfunction Detection.
S7.8.1 Simulate one or more ESC malfunction(s) by disconnecting the power source to any ESC component, or disconnecting any electrical connection between ESC components (with the vehicle power off). When simulating an ESC malfunction, the electrical connections for the telltale lamp(s) are not disconnected.
S7.8.2 With the vehicle initially stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “Start” position and start the engine. Place the vehicle in a forward gear and accelerate to 48 ±8 km/h (30 ±5 mph). Drive the vehicle for at least two minutes including at least one left and one right turning maneuver and at least one service brake application. Verify that, within two minutes of attaining this speed, the ESC malfunction indicator illuminates in accordance with S5.4.
S7.8.3 Stop the vehicle, deactivate the ignition locking system to the “Off” or “Lock” position. After a five-minute period, activate the vehicle's ignition locking system to the “Start” position and start the engine. Verify that the ESC malfunction indicator again illuminates to signal a malfunction and remains illuminated as long as the engine is running until the fault is corrected.
S7.8.4 Deactivate the ignition locking system to the “Off” or “Lock” position. Restore the ESC system to normal operation, activate the ignition system to the “Start” position and start the engine. Verify that the telltale has extinguished.
S7.9 Post Data Processing.
S7.9.1 Raw vehicle speed data is filtered with a 0.1 second running average filter.
S7.9.2 The torque data collected from the vehicle communication network or CAN bus as a digital signal does not get filtered. The torque data collected from the vehicle communication network or CAN bus as an analog signal is filtered with a 0.1-second running average.
S7.9.3 The activation point of the ESC engine torque reduction is the point where the measured driver demanded torque and the engine torque first begin to deviate from one another (engine torque decreases while the driver requested torque increases) during the Engine Torque Reduction Test. The torque values are obtained directly from the vehicle communication network or CAN bus. Torque values used to determine the activation point of the ESC engine torque reduction are interpolated.
S7.9.4 The time measurement for the J-Turn test maneuver is referenced to “time zero”, which is defined as the instant the center of the front tires of the vehicle reach the start gate, the line within the lane at zero degrees of radius arc angle. The completion of the maneuver occurs at the instant the center of the front tires of the vehicle reach the end gate, which is the line within the lane at 120 degrees of radius arc angle.
S7.9.5 Raw service brake pressure measurements are zeroed (calibrated). Zeroed brake pressure data are filtered with 0.1 second running average filters. Zeroed and filtered brake pressure data are dynamically offset corrected using a defined “zeroed range”. The “zeroing range” is defined as the 0.5 second time period prior to “time zero” defined in S7.9.4.
S8 Compliance Dates. Vehicles that are subject to this standard must meet the requirements of this standard according to the implementation schedule set forth in S8.
S8.1 Buses.
S8.1.1 All buses with a gross vehicle weight rating of greater than 14,969 kilograms (33,000 pounds) manufactured on or after June 24, 2018 must comply with this standard.
S8.1.2 All buses manufactured on or after August 1, 2019 must comply with this standard.
S8.2 Trucks.
S8.2.1 All three-axle truck tractors with a front axle that has a GAWR of 6,622 kilograms (14,600 pounds) or less and with two rear drive axles that have a combined GAWR of 20,412 kilograms (45,000 pounds) or less manufactured on or after August 1, 2017 must comply with this standard.
S8.2.2 All truck tractors manufactured on or after August 1, 2019 must comply with this standard.